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UNIVERSITY  OF  ILLINOIS 

Agricultural  Experiment  Station 


BULLETIN  NO.  116 


ON  THE  LIFE  HISTORY,  HABITS, 
AND  ECONOMIC  RELATIONS  OF  THE  WHITE- 
GRUBS  AND  MAY-BEETLES 


BY  S.  A.  FORBES 
STATE  ENTOMOLOGIST 


URBANA,  ILLINOIS,  AUGUST,  1907 


CONTENTS  OF  BULLETIN  No.   116. 

Introduction:     Subject  a  difficult  and  complicated  one 447 

The  economic  species 448 

Ivife  histories  of  the  injurious  species 449 

Lachnosterna  at  lights  and  on  trees  in  comparison 451 

Variation  of  numbers  in  different  localities  and  years 452 

Food  and  feeding  habits  of  the  species 454 

Results  of  feeding  experiments  with  May-beetles  {Lach- 
nosterna}   455 

Comparative  collections  of  Lachnosterna  from  food  plants, 

Urbana,  1906 456 

Movements  of  migration  and  dispersal 457 

Habits  of  reproduction 462 

Captures  of  Lachnosterna  at  light-traps,  open  fields, 

Urbana,  1906 463 

Collections  of  Lachnosterna  from  trees,  Urbana  1906 464 

Extract  from  breeding  cage  report 465 

Relations  to  weather 466 

Modes  and  places  of  hibernation ; 467 

Principal  enemies 468 

Swine 468 

Crows  and  blackbirds 468 

The  common  grub  wasp  (  Tiphia) 469 

Miscellaneous  insect  enemies 472 

Relation  to  soil  and  subsoil 476 

Relation  to  agricultural  management 477 

Injuries  to  crops 477 

Prevention  and  remedy 478 


ON  THE  LIFE  HISTORY,  HABITS,  AND  ECONOMIC  RE- 
LATIONS OF  THE  WHITE-GRUBS  AND  MAY- 
BEETLES  (LACHNOSTHRNA}. 

The  insects  generally  known  as  white-grubs  are  the  young,  or 
larvae,  of  the  large  brown  beetles  commonly  called  "June-bugs"  or 
May-beetles.  For  a  practical  knowledge  of  these  destructive  insects 
it  is  necessary  that  we  should  know  the  various  species  of  them 
which  do  serious  injury  to  agricultural  and  to  horticultural  crops; 
the  life  histories  of  all  these  species ;  their  relative  numbers  in  dif- 
ferent parts  of  the  state  in  different  years  and  in  different  periods 
of  years;  their  food,  both  as  grubs  and  as  adult  beetles,  including 
their  common  preferences  where  several  kinds  of  food  are  available 
to  them;  their  significant  habits,  especially  those  of  reproduction; 
their  relations  to  variety  of  weather  and  to  seasonal  change ;  their 
modes,  times,  and  places  of  hibernation;  the  range  of  their  daily 
movements  and  of  their  movements  of  migration  and  dispersal; 
their  enemies,  their  diseases — especially  those  of  a  contagious  char- 
acter, and  the  other  natural  checks  on  their  multiplication;  their 
relation  to  varieties  of  soil,  to  its  physical  condition,  its  moisture, 
and  its  exposure  to  the  sun ;  their  relation  to  varieties  of  the  subsoil 
also ;  the  effects  on  their  continuance  and  increase,  of  various  agri- 
cultural operations  and  kinds  of  farm  management ;  and  their  own 
effects,  under  varying  conditions,  on  the  several  kinds  of  crops  sub- 
ject to  injury  by  them.  Finally,  the  whole  field  of  preventive  and 
remedial  measures  of  a  more  or  less  artificial  character  must  be 
thoroughly  explored,  including  the  results  of  practical  experiments 
on  the  scale  of  actual  farm  management. 

The  subject  is  made  especially  difficult  and  complicated  by  sev- 
eral facts  and  circumstances.  There  are  many  species  of  these 
insects  recognizable  in  the  beetle  stage  but  seemingly  not  distinguish- 
able as  larvae ;  hence  one  frequently  can  not  tell  what  kind  of  grub 
he  is  dealing  with  until  he  has  reared  specimens  to  the  adult.  The 
life  history  of  these  insects  has  a  prolonged  cycle,  probably  of  three 
years,  but  just  how  many  is  not  definitely  known,  and  life  histories 
can  be  completed  only  by  keeping  specimens  alive,  under  more  or 
less  artificial  conditions,  for  this  entire  time.  The  various  species 
differ  sufficiently  in  certain  parts  of  their  life  histories  to  make  it 
necessary  to  follow  each  out  separately;  and  it  is  not  impossible 
that  important  differences  may  be  found  clue  to  differences  in  lati- 

447 


448  BULLETIN  No.  116.  .       [August, 

tude  and  climate,  between  northern  and  southern  Illinois;  hence 
each  species  must  be  studied  in  different  parts  of  the  state.  The 
most  important  species — that  is  the  most  abundant  ones — are  not 
the  same  in  all  parts  of  Illinois,  and  the  relative  importance  of  the 
various  species  must  be  made  out  for  each  region  separately.  The 
unexplained  sudden  disappearance,  several  times  noticed  by  us,  of 
nearly  the  whole  grub  population  of  badly  infested  fields  before 
their  transformation  to  the  pupa,  suggests  the  occurrence  among 
these  insects  of  contagious  diseases — a  supposition  borne  out  by  sev- 
eral field  and  insectary  observations ;  and  the  whole  subject  of  their 
bacterial  and  other  fungus  parasites  consequently  invites  attention. 
The  enormous  effect  of  the  rapid  multiplication,  under  favorable 
conditions,  of  certain  insect  parasites — a  hymenopterous  enemy, 
Tiphia  inornata,  especially — requires  a  critical  and  complete  study 
of  the  life  history  of  these  parasitic  insects  also,  especially  as  there 
is  some  probability  that  we  shall  be  able  to  increase  their  efficiency 
by  artificial  measures. 

No  one  has  heretofore  undertaken  to  work  out  to  a  finish  this 
difficult  but  highly  important  economic  problem,  and  our  present 
knowledge  of  the  white-grubs  is  a  patchwork  of  fragments,  contrib- 
uted by  a  considerable  number  of  observers  working  on  various 
species  and  in  different  parts  of  the  country.  The  nearest  approach 
thus  far  made  to  a  continuous  investigation  of  the  subject  was  car- 
ried on  in  this  office  in  the  years  of  1886-1890,  and  its  results  were 
published  in  1891  in  Volume  III.  of  "Insect  Life."* 

They  were  also  incorporated,  with  some  later  studies,  in  the 
Eighteenth  Report  of  the  Illinois  State  Entomologist,  printed  in 
1894.  In  the  year  1906  I  finally  began  what  I  now  hope  may  prove 
to  be  a  steady  and  comprehensive  study  of  this  problem  for  the 
state  of  Illinois ;  and  I  have  now  to  report  some  of  the  first  results 
of  this  work,  which  I  have  incorporated,  however,  with  other  data 
and  conclusions  in  a  way  to  give  us  a  fairly  full  synopsis  of  the 
present  state  of  our  knowledge,  and  a  clear  view,  consequently,  of 
its  deficiencies. 

THE  ECONOMIC  SPECIES. 

The  kinds  of  white-grubs  common  enough  in  Illinois  to  attract 
attention  because  of  their  injuries,  belong,  so  far  as  we  now  know,  to 
nine  species,  although  it  is  likely  that  this  list  would  be  longer  if  the 
injurious  grubs  of  southern  Illinois  were  as  well  known  to  us  as 
those  of  the  central  part  of  the  state.  Besides  these  nine  injurious 

*"On  the  Life  History  of  the  White-grubs."  By  S.  A.  Forbes.  Insect  Life,  Vol.  III.,  No. 
5,  pp.  239-245. 


1907.'}  WHITE-GRUBS  AND  MAY- BEETLES.  419 

grubs,  there  are  three  other  very  abundant  kinds  which  resemble 
closely  the  injurious  species,  although  they  are  themselves  harmless 
in  the  grub  stage. 

Eight  of  the  species  known  to  be  injurious  belong  to  the  genus 
Lachnosterna  and  one  to  the  genus  Cyclocephala.  Of  the  abundant 
but  harmless  grubs,  one,  frequently  called  the  muck-worm  because  it 
lives  in  stable  manure,  is  known  to  science  as  Ligyrus  relictus ;  an- 
other, called  the  carrot-beetle  in  the  adult  stage,  is  L.  gibbosa ;  and 
the  third  is  the  larva  of  the  green  June-bug  of  southern  Illinois  and 
of  the  Southern  States  generally,  known  in  the  beetle  stage  as  Allo- 
rhina  nitida.  All  the  last  three  species  are  injurious  as  beetles,  but 
only  one  of  them,  the  larva  of  the  carrot-beetle,  is  at  all  injurious  as 
a  grub,  and  then  only  slightly  or  occasionally  so.  The  eight  species 
of  Lachnosterna  known  to  be  injurious  in  Illinois  are  L.  fusca, 
rugosa,  inversa,  implicita,  gibbosa,  tristis,  ilicis,  and  hirticula ;  and 
the  injurious  Cyclocephala  is  C.  immaculata. 

Life  Histories  of  the  Injurious  Species. — The  life  histories  of 
the  white-grubs  of  the  genus  Lachnosterna  are  very  imperfectly 
known,  especially  as  to  the  length  of  time  required  for  the  growth 
and  development  of  a  complete  generation.  The  literature  of  the 
subject  records,  in  fact,  but  a  single  case  in  which  a  Lachnosterna 
has  been  reared  from  the  egg  to  the  adult.  An  egg  of  L.  arcuata 
laid  in  Washington  about  June  8,  1893,  hatched  in  approximately 
eleven  days,  and  changed  to  the  pupa  August  8,  1895,  and  to  the 
beetle  twenty-three  days  later.*  As  this  beetle  would  doubtless  have 
hibernated  in  the  earth  to  emerge  the  following  spring  and  lay  its 
eggs  in  June,  the  entire  period  from  the  egg  to  the  egg  again  was 
three  years.  This  is  the  length  of  the  life  cycle  which  has  com- 
monly been  inferred,  from  circumstantial  evidence,  for  our  species 
of  Lachnosterna  generally.  It  is  worthy  of  note,  however,  that  Melo- 
lontha  vulgaris,  the  European  white-grub  nearest  in  classification 
and  habits  to  our  American  species,  has  been  found,  according  to 
Xavier  Raspail,  to  have,  in  France,  a  period  of  three  or  four  years 
—the  shorter  period  if  the  years  are  moist  and  the  longer  one  if 
they  are  dry.f  In  Germany,  on  the  other  hand,  this  species  has  a 
four-year  period  at  the  north  and  a  three-year  period  at  the  south, 
with  various  occasional  exceptions  and  irregularities  of  appearance; 
and  a  related  species,  M.  hippocastani,  has  a  five-year  period  in  north 
Germany.  Our  American  species  of  Lachnosterna  will  probably  be 
found  to  present  similar  variations  of  life  history. 

*"BioIog-ir  Notes  on  the  May-beetle  Lar.hnosterna  arcuata  Sm."  By  F.  H.  Chittenden. 
Bull.  19,  N.  S.,  Div.  Ent.,  U.  S.  Dept.  Atrr.,  p.  77. 

tBull.de  la  Soc.  Zool.  de  France,  1891,  p.  271;  Mem.de  la  Soc.  Zool.  de  France,  1893,  T.  VI., 
p.  202. 


450  BULLETIN  No.  116.  [August, 

Whatever  the  length  of  life  in  the  grub  stage,  all  our  most 
abundant  species  of  Lachnosterna  begin  to  pupate  in  June  or  July 
in  central  Illinois,  and  begin  to  change  to  the  beetle  in  August  or 
September,  remaining,  with  rare  or  doubtful  individual  exceptions, 
under  ground  in  this  stage  until  the  following  March,  April,  or 
May.  They  then  emerge  from  their  winter  quarters,  feed  on  the 
leaves  of  various  trees,  and  pair  and  lay  their  eggs  in  the  earth  in 
June  and  July.  An  exception  should  perhaps  be  made,  provisionally, 
of  Z-.  tristis,  concerning  which  my  records  are  unusually  imperfect, 
agreeing,  so  far  as  they  go,  with  those  of  the  other  species  of  our 
list,  but  stopping-  short  before  the  middle  of  June.  That  is,  we  have 
an  abundance  of  the  beetles  collected  from  the  latter  part  of  March 
through  April  and  May  and  into  early  June,  most  frequently,  how- 
ever, in  May,  but  have  no  collections  in  any  stage  at  any  date  later 
than  June  5.  Four  of  our  lots  of  tristis,  collected  in  March  and 
April,  were  beetles  taken  from  the  earth,  which  must  have  trans- 
formed the  preceding  summer  or  fall. 

Pupae  of  the  above  species  have  been  taken  by  us  from  their 
underground  cells  only  in  June,  July,  August,  and  September,  and 
the  adult  beetles  have  been  found  under  ground  in  the  cells  where 
they  originated,  in  August,  September,  October,  and  November,  and 
again  in  April  and  early  May.  Adults  of  various  species  have  been 
seen  pairing  in  May,  and  in  one  case  in  June,  and  eggs  of  seven  of 
these  species — tristis  being  omitted — have  been  secured  in  June  and 
July,  much  the  greater  part  of  them  in  the  former  month.  So  far 
as  my  rather  scanty  records  go,  the  eggs  may  be  expected  to  hatch 
from  ten  days  to  four  weeks  from  the  time  of  deposit.  My  dates 
for  the  hatching  of  eggs  of  known  species  are,  for  inversa,  June  23 
and  July  n  ;  for  fuse  a,  June  27;  for  implicit  a,  July  16,  21,  and  24, 
and  August  7 ;  and  for  hirticula,  July  7. 

From  this  it  will  appear  that  white-grubs  found  in  the  earth 
beyond  the  middle  of  September  will  not  change  to  the  beetle  that 
year,  but,  barring  destruction  by  parasites  and  other  fatal  accidents, 
may  be  expected  to  pass  the  winter  as  grubs  and  to  continue  in 
that  stage  at  least  until  the  following  June.  This  is  a  point  of 
special  economic  interest,  since  the  owner  of  infested  fields  needs  to 
know  whether  the  grubs  in  the  ground  during  the  latter  part  of  the 
season  will  continue  there  in  dangerous  numbers  during  the  follow- 
ing spring,  or  whether  he  may  expect  relief  from  their  injuries  by 
reason  of  their  change  to  the  beetle. 

The  data  of  my  collections,  when  taken  in  the  aggregate  for 
several  years,  give  little  indication  of  any  fixed  order  of  succession 


1907.] 


WHITE-GRUBS  AND  MAY-BEETLES. 


451 


in  the  first  appearance  of  the  different  species  of  Lachnosterna  in 
spring1.  Inversa,  fusca,  rugosa,  hirticula,  and  tristis  have  all  been 
taken  by  us  in  the-  later  days  of  March,  and  gibbosa  on  April  6. 
Implicita  and  ilicis  have  made  their  first  appearances  about  a  month 
later  than  the  average,  but,  although  implicita  is  sometimes  excess- 
ively abundant,  these  two  species  have  been  much  less  frequently 
taken  by  us  than  the  others,  and  the  record  might  have  been  differ- 
ent if  the  collections  made  had  been  equally  numerous.  The  dates 
of  last  occurrence  are  also  nearly  the  same  for  these  species,  and 
their  periods  of  greatest  abundance  do  not  vary  greatly. 

Fusca,  however,  commonly  appears  in  large  numbers  at  electric 
lights  about  a  week  earlier  than  the  other  species,  and  gibbosa  is 
about  as  much  later  than  the  others — a  fortnight  later  than  fusca. 
Our  records  of  egg-laying  are  substantially  the  same  for  all  the 
seven  species  covered  by  them.  So  far,  consequently,  as  the  mere 
period  of  adult  activity  is  concerned,  these  insects  are  virtually  one 
species,  and  we  must  look  to  other  facts  and  conditions  for  any  spe- 
cific distinctions  of  habit  or  agricultural  relation. 

I  find  that  the  data  of  the  relative  abundance  and  dates  of  emer- 
gence of  the  various  species  derived  from  electric-light  collections 
disagree  widely  with  the  data  of  collections  made  from  the  food 
plants  of  the  beetles  at  the  same  time.  Apparently  some  of  the 
species  are  more  strongly  attracted  to  lights  than  others.  In  1891, 
and  again  in  1906,  collections  were  made  at  Urbana  from  trees  and 
from  lights  during  the  greater  part  of  the  active  period  of  the  May- 
beetles,  with  the  results  shown  in  the  following  table . 

LACHNOSTERNA  AT  LIGHTS  AND  ON  TREES,  IN  COMPARISON.  URBANA. 


18 

91 

19 

06 

Lights 

Trees 

Lights 

Trees 

No.  Specimens  

1874 

836 

142 

3484 

Iv.  gibbosa  

.02 

.02 

.00 

03 

Iv.  inversa  

.76 

.32 

.54 

00 

L.  dubia  

•00 

.00 

02 

00 

L/.  fusca   

05 

.23 

00 

01 

Iv.  rugosa  

.00 

.00 

24 

06 

Iv.  implicita  

.00 

.00 

15 

72 

Iv.  hirticula  

10 

42 

03 

07 

L/.  ilicis  

.00 

00 

02 

10 

Iv.  tristis  

\       .07 

.00 

.00 

.01 

452  BULLETIN  No.  116.  [August, 

In  1891,  when  1,874  specimens  were  taken  from  lights  and  836 
from  trees,  the  dominant  species  at  lights  was  inversa  (76  per  cent.), 
hirticula,  tristis,  and  fusca  following  with  ratios  of  10  per  cent.,  7 
per  cent.,  and  5  per  cent,  respectively.  The  dominant  species  from 
trees,  on  the  other  hand,  were  hirticula  (42  per  cent.),  inversa  (32 
per  cent.),  and  fusca  (23  per  cent.),  the  only  other  species  being 
gibbosa  (2  per  cent.).  The  results  for  1906,  when  142  specimens 
were  taken  at  lights  and  3,484  at  trees,  were  equally  discordant. 
The  leading  species  at  lights  this  year  was  inversa  (54  per  cent.), 
rugosa  and  implicita  following  with  24  per  cent,  and  15  per  cent, 
respectively;  while  the  leading  species  in  trees  was  implicita  (72 
per  cent.),  followed  by  ilicis  and  rugosa,  10  per  cent,  and  6  per  cent, 
respectively. 

Variation  of  Numbers  in  Different  Localities  and  Years. — The 
numbers  of  the  several  species  vary  greatly  from  year  to  year  in  the 
same  locality,  and  in  different  localities  during  the  same  season.  It 
consequently  happens  that  the  dominant  species  in  a  locality  may  be 
different  in  successive  years,  and  that  the  dominant  species  in  one 
locality  may  be  different  from  that  in  another,  within  the  same  year. 
Collections  have  not  been  made  on  a  large  enough  scale  or  in  suf- 
ficiently continuous  series  to  enable  us  to  exhibit  these  differences  in 
any  detail,  but  the  following  may  serve  as  illustrations : — 

Collections  made  at  a  street-lamp  in  Maywood,  near  Chicago,  by 
O.  S.  Westcott,*  on  seventeen  nights  from  May  9  to  June  14,  1887, 
contained  798  specimens  of  fusca  and  313  of  gibbosa — fusca  pre- 
dominating in  a  ratio  of  more  than  2*/£  to  i ;  and  collections  made 
the  following  year  at  the  same  place  by  the  same  person,  on  seven- 
teen nights  between  June  2  and  July  2,  gave  73  specimens  of  fusca 
•and  1,836  of  gibbosa — gibbosa  now  predominating  in  a  ratio  of 
25  to  I.  The  difference  in  the  collection  period  of  the  two  years 
was  due  to  the  difference  in  the  weather  of  the  spring,  which  was 
backward  and  stormy  in  1888.  If  we  compare  the  collections  of  the 
same  periods  for  these  two  years — June  9  to  14  in  1887,  and  June  9 
to  13  in  1888 — we  have  96  specimens  of  fusca  to  82  of  gibbosa  in 
1887,  and  29  of  fusca  to  1,020  of  gibbosa  in  1888. 

A  similar  comparison  may  be  made  between  the  contents  of  fre- 
quent collections  from  trees  made  at  Urbana  through  the  whole 
period  of  activity  of  the  May-beetles  in  1891  and  again  in  1906 — 836 
specimens  in  the  former  year  and  3,484  in  the  latter.  (See  table 
on  p.  451.)  In  the  collections  of  1891  the  dominant  species  were 
hirticula  (42  per  cent.),  inversa  (32  per  cent.),  and  fusca  (23  per 

*"Eotomologica  Americana,  Nov.,  1888,  Vol.  IV.,  p.  155. 


1907.]  WHITE-GRUBS  AND  MAY-BEETLES.  453 

cent.),  the  only  other  species  represented  being  gibbosa  (2  per  cent.). 
In  1906,  on  the  other  hand,  the  dominant  species  was  implicita  (72 
per  cent.),  the  remaining  species,  mentioned  in  the  order  of  their 
abundance,  being  ilicis  (10  per  cent.),  hirticula  (7  per  cent.),  rugosa 
(6  per  cent.),  gibbosa  (3  per  cent.),  and  fusca  and  tristis  (each  I 
per  cent.).  This  latter  comparison  is  vitiated,  however,  by  the  fact 
that  the  collections  were  made  from  different  kinds  of  trees,  those  of 
1891  mainly  from  butternuts  and  hickories,  and  those  of  1906  from 
poplars,  willows,  elms,  and  oaks, — another  example  of  the  fragmen- 
tary and  disjointed  character  of  the  data  now  available  for  a  study 
of  this  subject. 

It  so  happens  that  extensive  collections  of  May-beetles  were 
made  in  1888  both  in  Cook  county,  111.,  by  Westcott,  and  in  the  Dis- 
trict of  Columbia  by  J.  B.  Smith,*  and  a  comparison  of  the  relative 
numbers  of  the  dominant  species  in  these  two  widely  separate  locali- 
ties would  be  possible  by  their  means  if  it  were  not  for  the  fact  that 
Westcott's  specimens  were  all  taken  at  lights  and  Smith's  were  ob- 
tained from  trees  and  shrubs.  As  already  shown,  collections  are 
not  comparable  when  made  in  these  different  ways. 

Much  more  nearly  equivalent  collections  were  made  in  1906  by 
two  assistants  of  my  office,  one  working  at  Urbana,  in  Champaign 
county,  between  May  26  and  June  23,  and  the  other  at  Elliott,  in 
Ford  county,  between  May  23  and  June  5,  the  first  collecting  at 
lights  scattered  through  fields  of  grass  a  total  of  142  specimens  in 
ten  nights,  and  the  second  obtaining  at  a  single  light  in  a  large  corn 
field  389  specimens  in  six  nights.  At  Urbana  the  dominant  species 
was  inversa  (54  per  cent.)  ;  at  Elliott  it  was  gibbosa  (71  per  cent.). 
At  Urbana  gibbosa  was  not  taken  in  these  light-collections,  and  at 
Elliott  inversa  made  but  20  per  cent,  of  all  obtained. 

A  further  profitable  comparison  may  be  made  of  data  contrib- 
uted by  Prof.  M.  V.  Slingerland  from  the  product  of  light-traps 
kept  in  continuous  operation  at  Ithaca,  N.  Y.,  during  the  seasons  of 
1889  and  1892.1  Four  hundred  and  thirty-eight  specimens  of 
Lachnosterna  were  taken  during  the  first  of  these  years,  and  273 
during  the  second.  Fusca  was  much  the  most  abundant  species  in 
both  years,  making  76  per  cent,  of  the  product  of  the  traps  in  1889, 
and  90  per  cent,  in  1892.  Dubia  was  next  to  fusca  in  1889  (15  per 
cent.)  ;  and  this  species  and  ilicis,  each  4  per  cent.,  were  likewise 
next  to  fusca  in  1892.  The  similarity  of  the  records  for  these  two 
years  is  possibly  due  to  a  three-year  period  of  the  dominant  species, 

*"Proc.  U.  S.  National  Museum,  1888,  Vol.  II.,  p.  488. 
Canadian  Entoniolog-ist,  March,  1893,  Vol.  XXV.,  p   81. 


454  BULLETIN  No.  116.  [August, 

fusca,  but,  unfortunately,  as  no  comparable  collections  were  made 
in  the  intermediate  years,  the  evidence  is  not  complete.  Westcott's 
Maywood  collections,  already  referred  to,  on  the  other  hand,  hint  at 
a  two-year  period  for  L.  gibbosa.  This  species  predominated  over 
fusca  in  1886,  as  shown  by  records  made  on  five  nights,  from  the 
26th  of  May  to  the  ist  of  June,  in  a  ratio  of  3.6  to  I,  and  again  in 
1888,  in  a  ratio,  as  already  stated,  of  25  to  i,  but  was  much  less 
abundant  than  fusca  in  the  intermediate  year. 

FOOD  AND  FEEDING  HABITS  OF  THE  SPECIES. 

The  white-grubs  and  the  May-beetles,  larvae  and  adults  of  the 
same  insect  species,  differ  totally  in  their  food  and  feeding  habits, 
the  grubs  eating  the  roots  of  various  kinds  of  plants  and  the  beetles 
eating  the  leaves  of  trees  and  shrubs.  In  the  absence  of  any  means 
of  distinguishing  the  species  one  from  another  in  the  grub  stage,  no 
evidence  has  been  obtained  of  any  special  choice,  by  any  of  the 
species  in  this  stage,  among  the  various  elements  of  the  food  of 
grubs  in  general.  So  far  as  known,  all  of  them  may  take,  with 
equal  relish,  all  kinds  of  food  which  any  one  of  them  will  eat.  If 
the  different  species  of  grubs  do  indeed  make  definite  and  varied 
choice  of  food,  the  fact  may  be  ascertained  by  breeding  to  the  adult, 
for  determination,  pupae  and  full-grown  grubs  obtained  in  various 
situations  near  or  among  different  kinds  of  food  plants;  but  there 
is  at  present  too  little  recorded  information  on  this  point  to  permit 
us  to  infer  any  difference  whatever  in  the  choices  of  our  more 
abundant  species. 

The  species  of  beetles  themselves,  on  the  other  hand,  differ  con- 
siderably, although  not  sharply  and  completely,  as  a  rule,  in  their 
choices  of  food  where  several  kinds  are  equally  accessible  to  them. 
Evidence  of  these  preferences  has  been  obtained  by  us  in  three  dif- 
ferent ways:  (i)  by  experimental  feedings  with  beetles  kept  in 
confinement;  (2)  by  parallel  collections  of  beetles  made  from  dif- 
ferent kinds  of  food  plants;  and  (3)  by  the  dissection  of  specimens 
of  various  species,  made  to  determine,  by  an  examination  of  the 
contents  of  their  alimentary  canals,  what  kind  of  vegetation  they 
have  been  feeding  on.  The  first  method  shows  what  the  beetles  may 
eat  under  stress  of  hunger,  or  perhaps  with  starvation  as  a  penalty 
for  refusing  what  is  offered  them ;  the  second  shows  what  the  dif- 
ferent species  actually  choose  when  a  choice  is  open  to  them;  and 
the  third  enables  us  to  determine  with  certainty  what  the  beetles 
have  eaten  where  direct  observation  is  impracticable.  The  results 
of  our  feeding  experiments  have  been  so  different  from  those  ob- 


1907.} 


WHITE-GRUBS  AND  MAY-BEETLES. 


455 


tained  by  making  collections  from  the  food  plants  at  night  that  they 
evidently  have  comparatively  little  real  value.  For  example,  leaves 
of  Osage  orange  were  offered,  without  other  food,  to  fusca,  inversa, 
implicita,  ilicis,  rugosa,  and  tristis.  They  were  eaten  moderately 
by  implicita  and  rugosa,  and  slightly  by  fusca,  inversa,  and  ilifis, 
but  were  constantly  refused  by  tristis.  On  the  other  hand,  extensive 
observations  made  in  the  field  have  given  us  no  instance  of  actual 
feeding  on  this  plant  in  the  open  air  by  any  of  our  species,  although 
it  is  ever}; where  in  common  use  as  "a  hedge  plant. 

The  following  table  shows  the  different  kinds  of  food  offered  to 
Lachnosterna  beetles  in  breeding-cages  in  1904  and  1905,  and  data 
as  to  the  readiness  with  which  each  sort  of  leaf  was  eaten  when 
but  one  kind  of  food  was  placed  in  the  cage. 

RESULTS  OF  FEEDING  EXPERIMENTS  WITH 
MAY-BEETLES  (LACHNOSTERNA).. 


- 

Gibbosa 

Inversa 

rt 
o 
• 

3 
fc 

Rug-osa 

Implicita 

Hirticula 

• 
°o 

M 

Tristis 

Average 

Carolina  Poplar, 

(Populus  moniliftra)  . 

1 

3 

3 

3 

3 

3 

3 

2 

2]62 

Willow  

_ 

.     3 

3 

2 

3 

_ 

3 

1 

2.iO 

Oak  

2 

3 

2 

2 

3 

3 

2.50 

E}lm  

3 

2 

3 

2 

2 

3 

3 

3 

2.62 

Apple    

1 

2 

3 

3 

3 

3 

3 

1 

2.37 

Box-elder  

1 

2 

3 

1 

3 

2 

2 

0 

1.75 

Plum  

1 

0 

3 

0 

3 

3 

2 

0 

1.50 

Peach  

1 

0 

1 

0 

1 

1 

1 

0 

.71 

White  Ash  

1 

-7 

1 

1 

3 

2 

1 

0 

1.57 

Tulip  tree, 

(Liriodendron)  .  . 

0 

1 

1 

0 

1 

1 

0 

0 

.57 

Hedtre  .  . 

_ 

1 

1 

2 

2 

_ 

1 

0 

1.40 

L/ilac  

_ 

1 

2 

1 

_ 

1.33 

Cherry  

1 

1 

1 

1. 

Corn  

_ 

2 

2 

2 

2 

_ 

1 

0 

1.50 

Grass.  . 

_ 

2 

2 

2 

1 

_ 

1 

0 

1.60 

l=slig'htly  eaten,  2  =tnoderately  eaten,  3  =  freely  eaten,  0  =  refused  to  eat,    -  =  not  offered. 

An  attempt  was  also  made  to  test  the  general  food  preferences 
of  each  species  by  offering  several  different  kinds  of  food  in  the  cage 
at  once.  Under  these  conditions,  L.  fusca,  inversa,  and  implicita 
ate  most  freely  of  Carolina  poplar  and  willow ;  L.  ilicis  and  hirticula 
ate  most  freely  of  oak,  but  freely,  also,  of  Carolina  poplar  and  dm ; 
and  L.  tristis  ate  only  oak  when  that  was  present.  L.  rugosa  se- 
lected poplar  and  elm,  and  L.  gibbosa,  oak  and  elm. 

In  1906,  at  Urbana,  extensive  collections  were  made  with  equal 
care  from  each  of  the  four  different  kinds  of  trees  which  May-beetles 


456 


BULLETIN  No.  116. 


[August, 


seemed  to  prefer  as  food.  The  beetles  were  gathered  by  shaking 
them  from  the  trees  at  night  and  picking  up  those  which  fell  to 
the  ground. 

The  following  table  gives  the  results  of  these  collections  made 
at  Urbana  from  Carolina  poplar  (cotton wood),  willow,  oak,  and 
elm,  on  twenty-six  different  nights  between  May  14  and  June  28, 
1906. 

COMPARATIVE  COLLECTIONS  OF  LACHNOSTERNA  FROM  FOOD 
PLANTS.     URBANA,  1906. 


Species 

Poplar 

Willow 

Oak 

Elm 

• 

No. 

Per 
cent. 

No. 

Per 
cent. 

No. 

Per 
cent. 

No. 

Per 

cent. 

L/.  implicita  

1456 
169 

73 
39 
10 

5 
2 

.58 
.85 

.72 
.85 
.04 

855 

7 
6 
6 
4 
1 

.34 

.07 
.13 
.03 

35 

18 
1 
209 

2 
317 

25 

.01 

.17 
.02 
.86 

.93 
1.00 

171 
31 

4 

17 
21 

.07 
.15 
.04 

.07 
.07 

L/.  mgosa  

L/    gibbosa  

L/.  f  usca  

L/.  hirticnla  

L/.  ilicis  

L/.  tristis  

Total  

1754 
.50 

879 

.25 

607 
.18 

f 

244 
.07 

Per  cent,  on  each  tree 

From  the  foregoing  table  it  will  be  seen  that  poplar  (cotton- 
wood)  was  the  favorite  food,  50  per  cent,  of  the  specimens  being 
taken  from  this  tree,  and  that  willow  follows  next  with  25  per  cent., 
oak  with  18  per  cent.,  and  elm  with  7  per  cent.,  poplar  and  willow 
together  yielding  75  per  cent,  of  the  insects.  Apple  leaves  were 
often  eaten  freely,  but  no  trees  were  suitably  situated  for  experimen- 
tal field-collecting,  and  hence  no  comparative  records  were  made 
which  included  apple.  Apple  orchards  in  the  southern  part  of  the 
state  have  been  reported  by  assistants  as  sometimes  almost  stripped 
of  their  leaves.  This  was  notably  so  in  Jackson  county  in  1904. 
The  pecan-  and  persimmon-trees  of  southern  Illinois  often  suffer 
severely  by  having  their  foliage  eaten  by  the  beetles. 

Certain  species  of  the  beetles  exhibited  marked  preferences  in 
the  choice  of  food.  L.  hirticula,  ilicis,  and  tristis  had  a  special  liking 
for  oak,  the  last  named  being  taken  from  no  other  tree.  L.  implicita, 
gibbosa,  fusca,  and  ntgosa  were  most  abundant  on  poplar,  rugosa 
seeming  to  avoid  oak  and  willow.  Not  enough  specimens  of  L,.  in- 
versa  were  taken  to  warrant  conclusion's  concerning  its  preferences. 

All  of  the  May-beetles  taken  at  lights  in  the  open  fields  at  night 
in  1906  at  Elliott,  Ford  county,  and  at  Urbana,  Champaign  county, 
were  carefully  dissected  and  the  contents  of  the  alimentary  canals 


1907.]  WHITE-GRUBS  AND  MAY-BEETLES.  45*7 

were  examined  microscopically.  Nearly  40  per  cent,  of  all  the 
May-beetles  taken  had  eaten  nothing.  This  percentage  was  much 
the  highest  for  specimens  taken  early  in  the  season,  62  per  cent.,  for 
example,  for  those  caught  before  June  6.  Probably  most  of  these 
empty  beetles  had  just  come  from  the  earth  and  had  not  yet  begun 
to  feed.  Nearly  all  of  those  captured  in  the  fields  .at  lights  which 
had  taken  food  had  eaten  the  leaves  of  trees,  as  was  shown  by  the 
presence  in  their  intestines  of  small  pieces  of  leaves  exhibiting  the 
netted  vein-structure  and  other  characteristics  of  the  foliage  of  the 
common  trees  of  the  vicinity.  Only  six  specimens  of  about  six  hun- 
dred dissected,  had  eaten  the  leaves  of  young  corn.  Five  of  these 
specimens  belonged  to  L.  rugosa  and  the  sixth  to  L.  inversa.  Four 
additional  specimens  of  L.  rugosa  were  taken  at  Urbana  directly 
from  corn  while  feeding  on  it.  As  these  ten  beetles  represent  only 
about  i^4  Per  cent.  of  the  whole  number  examined,  the  facts  indi- 
cated by  them  are  of  little  economic  significance  except  as  going  to 
show  that  May-beetles,  of  these  two  species  at  least,  emerging  in 
corn  fields  at  a  distance  from  trees  too  great  to  enable  them  to  find 
their  more  ordinary  food,  may  nevertheless  subsist  on  leaves  of 
corn.  The  same  facts  have  been  shown  with  reference  to  blue-grass, 
and  it  seems  probable  that,  in  the  absence  of  other  food,  beetles  may 
be  able  to  live  on  the  blue-grass  of  our  pastures.  With  their  actual 
powers  of  flight  and  their  strong  disposition  to  assemble  in  trees  at 
night,  not  merely  to  feed  but  likewise  to  copulate,  their  ability  to 
feed  on  grass  and  corn  seems  to  signify  but  little.  Corn,  oats,  wheat, 
clover,  and  grass  fields  were  repeatedly  examined  in  both  Ford  and 
Champaign  counties  with  a  view  to  the  detection  of  any  injury 
which  might  have  been  caused  by  these  beetles.  Occasionally  at 
Urbana,  and  more  frequently  at  Elliott,  corn  plants  were  found 
which,  though  uninjured  in  the  evening-,  were  partially  eaten  by  the 
next  morning,  and,  as  already  mentioned,  four  May-beetles  (Z,. 
rugosa)  were  taken  directly  from  the  plants  while  feeding  on  them. 
Dissection  of  these  specimens  showed  beyond  a  doubt  that  they  had 
eaten  the  leaves  of  corn.  Two  hundred  and  sixty-two  specimens  of 
this  species  were  taken  in  1906,  169  of  them  from  poplar,  31  from 
elm,  and  62  from  other  situations,  and  only  9  of  these  had  eaten 
corn,  as  biiown  by  dissection. 

MOVEMENTS  OE  MIGRATION  AND  DISPERSAL. 

As  the  larvse  known  as  white-grubs  never  appear  above  ground 
except  by  accident,  and  as  they  are  sluggish  insects,  incapable  of 
rapid  locomotion  under  ground,  each  is  practically  confined,  so  far  as 


458  BULLETIN  No.  116.  [August, 

we  now  know,  to  the  immediate  neighborhood  of  its  origin.  The 
grubs  change  location  slowly  as  their  food  is  exhausted,  and  injured 
spots  in  an  infested  lawn  or  grain  field  will  gradually  enlarge  in  all 
directions,  the  white-grubs  moving  outwards  into  fresh  pasturage 
as  the  infested  vegetation  dies  from  the  destruction  of  its  roots.  The 
grubs  also  sometimes  gather  in  from  all  directions  towards  a  par- 
ticularly attractive  patch  of  their  food  plants ;  but  there  is  nothing 
to  show  that  they  move  from  place  to  place  by  definite  underground 
migration,  or  that  they  cover  any  considerable  distance,  such  as  to 
take  them  from  one  field  to  another,  during  the  whole  period  of  their 
active  larval  life. 

The  May-beetles  also  seem  local  in  their  distribution.  Although 
very  good  fliers,  they  use  their  wings  only  to  carry  them  from  their 
place  of  origin  to  the  trees  and  shrubs  on  which  they  feed  and  in 
which  they  copulate  at  night,  and  from  these  to  their  daytime  hid- 
ing places,  never  moving  in  swarms,  so  far  as  known,  or  migrating 
over  considerable  distances.  There  is,  in  short,  no  evidence  of  any 
migration  movement  of  this  insect  in  any  stage  or  under  any  cir- 
cumstances, but  each  locality  or  considerable  neighborhood  prob- 
ably breeds  and  maintains  its  own  white-grub  population  year  after 
year.  Their  most  marked  movements  are  the  evening  flight  of  the 
beetles  to  their  food  plants,  and  the  morning  dispersal  from  trees 
to  the  fields  in  which  the  females  lay  their  eggs. 

The  discovery  that  certain  species,  at  least,  of  the  May-beetles 
may  feed,  and  sometimes  do  feed  to  a  small  extent,  on  corn  and 
grass,  and  the^  consequent  conclusion  that  they  may  not  need  con- 
venient access  to  trees  for  food,  raises  the  important  question 
whether  some  of  these  insects,  and  possibly  certain  species  of  them, 
may  not  live  continuously  in  the  fields,  feeding  on  the  crop  plants 
there  and  laying  their  eggs  in  the  very  places  where  they  themselves 
originated.  If  this  is  the  case,  collections  made  in  the  fields  at  max- 
i.-.ium  distances  from  trees  should  give  us  proof  of  the  fact;  and  I 
consequently  arranged,  in  the  spring  of  1906,  for  the  systematic  use 
of  lantern  traps  distributed  over  an  open  area  of  one  hundred  and 
sixty  acres  on  the  main  farm  of  the  University  of  Illinois,  with  trees 
of  various  sorts  in  a  cemetery  along  one  side  of  this  tract,  and  no 
others  within  less  than  half  a  mile  from  it  in  any  direction.  These 
traps  were  ordinary  kerosene  lanterns,  with  glass  globes,  placed 
over  large  tin  trays,  each  containing  kerosene  to  a  depth  of  about 
half  an  inch.  These  trays  were  not  large  enough  to  secure  all  the 
beetles  which  flew  against  the  lantern  globes,  but  they  nevertheless 
gave  satisfactory  samples  of  the  beetles  flying  in  the  field. 


1907.} 


WHITE-GRUBS  AND  MAY-BEETLES. 


4o9 


The  accompanying  plat  shows  the  crops  of  this  tract  and  the  dis- 
tribution of  the  lantern  traps  in  each.  Forty  acres  were  in  corn, 
seventy  acres  in  grass,  thirty  acres  in  clover  and  alfalfa,  and  twenty 
acres  in  oats.  Two  of  the  lanterns  were  in  corn  fields,  two  in  clover 

Plat  showing  Distribution  of  Light-traps. 


Cemetery 


Road 


Road 


New  pasture 
20  acres 


Oats 
20  acres 


Old  pasture 
40  acres 


Alfalfa 
20  acres 


•  Clover 
10  acres 


Corn 
20  acres 


Meadow  grass 
10  acres 


Corn 
20  acres 


and  alfalfa,  one  in  oats,  and  seven  in  meadows  and  pastures  of  grass. 
None  were  nearer  than  a  quarter  of  a  mile  to  trees  on  whose  leaves 
the  May-beetles  were  feeding  at  the  time,  nor  farther  from  them 
than  three  quarters.  To  avoid  attracting  beetles  from  these  trees, 
each  lantern  was  provided  with  a  tin  shade  by  which  its  light  was 
hidden  on  the  side  towards  the  trees  nearest  to  it.  These  lights  were 


460  BULLETIN  No.  116.  [August, 

kept  burning  all  night  for  fourteen  nights  between  May  20  and  June 
23  inclusive,  and  were  visited  at  frequent  intervals  during  each  of 
these  nights.  The  weather  was  so  cold  during  four  nights  that  the 
May-beetles  were  not  flying,  and  no  account  is  taken  of  these  nights 
in  this  discussion. 

The  total  product  of  the  twelve  traps,  thus  maintained  for  ten 
entire  nights,  was  142  specimens  of  May-beetles  of  the  genus  Lach- 
nostcrna  and  25  specimens  of  Cyclocephala.  No  account  is  taken  of 
the  latter  because  their  food  habits  are  very  different  from  those  of 
Lachnostcrna.  The  average  product  of  a  lantern  in  one  night  was 
only  1.2  of  the  true  May-beetles  (Lachnosterna),  and  the  largest 
catch  of  any  one  night  was  40  specimens  on  June  18,  or  3^3  per  light. 
The  largest  collections  were  made  on  three  nights  between  June  9 
and  1 8  inclusive,  these  averaging  33  per  night,  or  about  3  to  each 
trap.  The  two  collections  of  May,  made  on  the  26th  and  3ist  of 
the  month,  averaged  only  6  beetles  per  night,  or  i  to  each  two  traps. 

A  single  light-trap  of  the  same  kind,  exposed  at  night  withoyt  a 
screen,  for  ten  minutes  May  21  and  for  thirty  minutes  May  23,  close 
to  willow-trees  at  the  border  of  this  field  and  near  the  cemetery 
above  mentioned,  yielded  1 1  May-beetles  on  the  first  night  and  127  on 
the  second — seventy  times  as  many  taken  in  ten  minutes  by  one  trap 
near  these  trees  as  were  taken  at  approximately  the  same  date  by  a 
trap  exposed  all  night  in  the  open  field.  There  could  be  no  question, 
consequently,  that  very  nearly  all  the  May-beetles  of  this  neighbor- 
hood were  concentrated  in  the  trees  at  this  time. 

New  data  have  been  obtained  by  our  collections  and  observations 
of  recent  years  with  regard  to  the  nightly  movements  of  the  beetles, 
and  these  are  thus  summarized  by  Mr.  J.  A.  West,  who  had  charge 
of  this  work  for  1906. 

"There  is  a  regular  migration  of  beetles  from  the  fields  to  the 
trees  in  the  evening.  It  takes  place  in  June  just  about  dusk — from  a 
few  minutes  before  to  a  few  minutes  after  eight  p.  m.  The  move- 
ment of  the  beetles  is  almost  simultaneous  from  the  different  fields. 
An  observer  in  one  field  can  scarcely  move  to  another  and  hope  to 
see  the  migration.  It  is  usually  but  a  few  seconds  from  the  time 
its  beginning  is  noticed  in  one  place  until  a  companion  observer  will 
report  its  commencement  perhaps  a  quarter  of  a  mile  away.  Beetles 
were  found  rising  from  the  ground  in  fields  of  oats,  in  pasture,  old 
meadow,  clover,  alfalfa,  and  in  corn.  They  were  most  abundant  from 
old  pasture  and  least  numerous  from  alfalfa  and  corn.  They  were 
observed  coming  from  the  ground  in  considerable  numbers  in  oats 
and  clover  fields.  The  following  species  are  mentioned  in  the  order 


1907.]  WHITE-GRUBS  AND  MAY-BEETLES.  461 

of  their  abundance :  L.  implicita,  hirticula,  ilicis,  and  rugosa.  The 
evening  migration  occupies  not  over  fifteen  or  twenty  minutes,  and 
in  every  instance  it  seemed  completed  by  8 :  20  p.  m. 

"While  the  evening  migration  seemed  to  result  in  a  complete 
abandonment  of  the  fields  by  the  beetles,  yet  the  observer  may  now 
and  then  hear  a  beetle  whirr  past  in  the  darkness  at  any  hour  of  the 
night,  and  light-traps  so  placed  in  the  open  field  as  not  to  attract 
those  from  the  trees  will  take  specimens  in  small  numbers  through- 
out the  night.  The  beetles  distribute  themselves  regularly  over 
large  areas  when  they  leave  the  feeding  grounds  in  the  morning. 
The  following  is  a  record  of  specimens  taken  in  the  fields  a  quarter 
of  a  mile  or  more  from  trees,  and  apparently  coming  directly  from 
them:  L.  implicita,  n,  L.  hirticula,  5,  L.  rugosa,  31, — total,  47. 

All  these  specimens  were  taken  by  hand,  the  light-traps  not 
seeming  to  attract  them. 

"The  morning  movement  is  very  early.  It  varies  considerably, 
according  to  the  clearness  of  the  sky.  It  is  so  related  to  the  awaken- 
ing of  the  birds  that  it  seems  as  if  the  first  note  of  the  dick-cissel,  or 
other  early  bird,  is  the  signal  for  the  beetles  to  fly  to  their  hiding 
places  in  the  ground.  On  only  two  mornings  were  beetles  taken  in 
June  after  four  o'clock.  June  18,  a  dark  cloudy  morning,  a  pair 
of  L.  rugosa  were  taken  at  4 :  25  a.  m.  while  in  copulation  on  a  stem 
of  grass.  Ordinarily  the  movement  did  not  last  over  fifteen  min- 
utes and  it  very  rarely  continued  for  twenty  minutes.  On  the  morn- 
ing of  June  7,  however,  a  strong  wind  was  blowing  thirteen  to  four- 
teen miles  an  hour  from  the  south.  This  greatly  retarded  the 
flight  of  the  beetles  which  had  been  feeding  on  trees  to  the  north  of 
the  fields,  and  on  this  morning  it  began  at  3:35  o'clock  and  con- 
tinued until  4:10,  when  the  last  beetle  seen  was  taken  in  flight. 

"The  following  notes  show  the  variation  in  the  time  of  the 
morning  movement  of  the  beetles  according  to  the  brightness  of  the 
morning  and  its  relation  to  the  awakening  of  the  birds : — 

"Morning  of  June  10,  moonlight  and  very  bright.  Dick-cissel 
heard  at  3  :  08 ;  meadow-lark  at  3  :  15;  kingbird  at  3  :  20 ;  the  follow- 
ing, in  order  given,  from  3:25-3:35, — prairie-chicken,  brown 
thrasher,  quail,  robin,  and  horned  lark.  On  this  morning  the  beetle- 
movement  began  at  3 :  18  and  lasted  until  3 :  30. 

"Morning  of  June  18,  very  cloudy  and  dark.  No  bird  was  heard 
until  3  :  40,  and  the  movement  of  the  beetles  began  at  3  :  45  and  was 
complete  in  ten  minutes.  About  3  :  30  a.m.  was  the  average  time  for 
the  first  bird  note,  and  3  :  35-3  :  45  the  regulation  time  for  the  morn- 
ing movement  of  the  beetles." 


462  BULLETIN  No.  116.  [August, 

These  data  are  of  special  importance  as  showing  the  time  of 
night  when  the  beetles  are  accessible  in  the  trees  on  which  they 
feed — a  subject  important  to  a  discussion  of  measures  of  prevention 
and  remedy. 

HABITS  OF  REPRODUCTION. 

With  respect  to  the  reproduction  of  May-beetles,  we  need  to 
know  at  what  time  of  day,  in  what  situations,  and  especially  how 
soon  after  emerging,  the  sexes  pair,  and  when,  where,  how  soon,  and 
in  what  numbers  the  females  deposit  their  eggs.  Our  definite  infor- 
mation as  to  the  pairing  of  the  beetles  is  not  abundant,  but  is  suffi- 
cient to  show  that  they  pair  at  night  on  their  food  plants.  The  males 
are  much  more  active  than  the  females, — a  fact  illustrated  by  their 
greater  abundance  at  lights  in  fields  at  a  distance  from  trees.  In 
the  product  of  the  light-traps  used  in  1906,  as  described  in  this  paper 
under  "Movements  of  Migration  and  Dispersal,"  pp.  458-460), 
the  males  outnumbered  the  females  about  4  to  I,  while  in  collections 
made  at  the  same  time  from  trees  the  number  of  males  was  only 
39  per  cent,  of  the  total  number  taken.  Similar  data  were  given 
in  my  Seventh  Report.*  It  will  be  seen  that  it  does  not  follow  from 
the  greater  number  of  females  taken  on  the  food  plants  that  females 
are  actually  more  numerous  than  males,  but  only  that  the  latter  are 
more  widely  scattered  at  night,  and  more  generally  on  the  wing. 

It  has  been  noticed  by  some  of  the  office  assistants,  and  par- 
ticularly by  Mr.  J.  A.  West,  that  May-beetles  are  sometimes  very  un- 
equally numerous  in  neighboring  trees  of  the  same  kind,  one  tree 
containing  a  buzzing  multitude  while  there  are  comparatively  few 
on  another  tree  of  the  same  species  close  by.  I  have  myself  once 
seen  a  large  tree  so  full  of  May-beetles  in  the  evening  that  the  noise 
of  their  movements  was  like  that  of  a  huge  swarm  of  bees,  although 
the  condition  of  the  leaves  the  following  day  showed  that  they  had 
not  resorted  to  this  tree  for  food.  Their  assemblage  in  tree-tops  is 
evidently  in  part  for  breeding  purposes,  and  not  wholly  for  food. 

About  fifty  pairs  of  these  beetles  have  been  taken  by  us  in 
copula,  all  but  three  of  them  from  trees  at  night.  In  one  case  a  pair 
of.Z,.  rugosa  was  captured  at  night  by  Mr.  West  from  a  grass-blade 
in  a  pasture,  and  two  pairs  of  L.  inversa  have  been  seen  copulating 
in  a  breeding-cage,  also  at  night.  These  two  pairs  had  been  taken 
from  earthen  cells  in  the  ground  October  5,  1905,  and  transferred  to 
the  insectary,  where  they  at  once  went  into  the  earth,  first  appearing 
above  ground  on  the  ist  of  the  following  May.  They  began  to  feed 

*Eighteenth  Rep.  State  Ent.  III.,  p.  117. 


1907.] 


WHITE-GRUBS  AND  MAY- BEETLES. 


463 


on  elm  leaves  May  17,  and  paired  at  midnight  May  25.     Our  ob- 
served dates  of  copulation  all  fall  within  the  month  of  May. 

The  several  species  of  May-beetles  may  continue  active,  in  a  nor- 
mal season,  from  one  to  two  months,  reckoning  this  period  from  the 
first  appearance  of  the  earliest  specimens  to  emerge  to  the  final  disap- 
pearance of  the  beetles  for  the  year.  In  our  work  of  1906  the  dates 
of  first  and  last  appearance  of  the  more  abundant  species  in  collec- 
tions made  regularly  near  Urbana,  at  night,  from  willow,  oak,  elm, 
and  cottonwood  (Carolina  poplar),  were  as  follows:  L.  implicita, 
May  13*  and  June  28  (46  days)  ;  L.  ilicis,  May  21  and  June  23 
(33  days)  ;  and  L.  hirticula,  May  23  and  June  18  (26  days).  In 
New  York,  on  the  other  hand,  Professor  Slingerland  some  years 
ago  obtained  L.  fusca  in  his  light-traps  from  May  6  to  July  5,  1889, 
and  from  May  26  to  June  28,  1892 ;  L.  dubia  from  May  8  to  July  5, 
and  from  May  30  to  June  22 ;  and  L.  ilicis  from  June  I  to  July  30. 

CAPTURES  OF  LACHNOSTERNA  AT  LIGHT-TRAPS,  OPEN 
FIELDS,  URBANA,  1906. 


Inversa 

Implicita 

rt 

3 

3 

O 

Hirticula 

Rug-osa 

a> 

3 

01 

u 

"d 

X 

Females 

May  26  

4 

4 

o 

May  31  

6 

1 

1 

5 

3 

June    2  

8 

3 

5 

6 

June    4  

6 

1 

3 

4 

8 

6 

June    6  

2 

3 

4 

1 

June    9  

18 

1 

1 

2 

7 

9 

25 

6 

June  15  

22 

5 

24 

3 

June  18  

16 

9 

15 

40 

0 

June  20  

i 

0 

1 

June  23  

1 

0 

1 

Total  .  . 

76 

21 

3 

5 

34 

3 

115 

27 

Collections  made  only  from  the  food  plants  commonly  show  a 
more  rapid  diminution  and  earlier  disappearance  of  males  than  of 
females.  We  may  take  as  an  example  2517  specimens  of  L.  implicita 
collected  from  trees  on  twenty-six  different  nights  between  May  14 
and  June  28,  1906.  Thirty-nine  per  cent,  of  the  specimens  taken 
during  the  first  thirteen  days  were  males  and  only  15  per  cent,  of 
those  taken  during  the  last  thirteen  days.  On  the  other  hand,  in 
collections  made  during  the  same  period  by  means  of  lantern  traps 


*The  spring  was  unusually  late  this  year,  and  Ma3'-beetles  did  not  appear  on  the  wing- 
until  May  13. 


464 


BULLETIN  No.  116. 


[August, 


scattered  through  the  open  fields,  at  a  distance  from  the  food  plants 
of  the  beetles,  the  ratio  of  males  to  females  was  precisely  twice  as 
great  during  the  last  half  of  the  period  as  during  the  first.  Slinger- 
land's  data,  already  referred  to,  do  not  support  the  supposition  of 
a  relatively  early  death  of  the  males.  It  seems  likely,  consequently, 
that  females  may  require  repeated  fertilization,  especially  as  the 
eggs  are  laid  gradually,  a  few  at  a  time. 


COLLECTIONS  OF  LACHNOSTERNA  FROM  TREES,  URBANA,  1906. 


Implicita 

Fusca 

Gihbosa 

Rug-osa 

Ilicis 

Hirticula 

Inversa 

Tristis 

0 

V 

0) 

0 

<0 

0) 

rt 

rt 

a 

~* 

ri 

a 

ri 

a 

s 

n 

& 

fi 

a 

g 

fi 

£ 

g 

n 

t) 

rt 

u 

<u 

« 

V 

« 

ctf 

u 

<u 

8 

fa 

« 

fa 

% 

fa 

% 

fa 

8 

•  fa 

E 

fa 

* 

fa 

H 

fa 

May  14.  . 

59 

90 

3 

1 

May  15..    .. 

74 

95 

8 

2 

May  16.  . 

27 

52 

5 

3 

May  17..    .. 

109 

200 

1 

May  21.  . 

24 

23 

1 

May  22  ... 

19 

25 

10 

2 

1 

May  23.  . 

193 

239 

7 

7 

8 

2 

3 

14 

5 

2 

1 

May  24.  . 

25 

26 

2 

5 

1 

2 

2 

May  25..    .. 

31 

35 

May  26..    .. 

104 

135 

5 

4 

4 

1 

13 

9 

3 

1 

1 

1 

May  30.  . 

4 

25 

6 

5 

1 

2 

May  31..    .. 

50 

108 

17 

2 

28 

24 

45 

21 

6 

5 

June    1..    .. 

24 

125 

4 

3 

12 

6 

3 

1 

June    2.  . 

45 

129 

8 

8 

12 

4 

June    4.  . 

14 

96 

3 

19 

14 

5 

16 

3 

1 

June    5.  . 

6 

54 

1 

24 

24 

12 

20 

1 

3 

June    6.  . 

4 

36 

15 

2 

3 

8 

12 

3 

6 

3 

June    7..    .. 

1 

9 

20 

16 

4 

17 

12 

5 

7 

7 

June    9.  . 

5 

41 

14 

16 

15 

8 

6 

4 

June  15.. 

4 

27 

7 

13 

21 

39 

8 

12 

June  16..    .. 

17 

13 

17 

4 

1 

1 

2 

June  18  ... 

12 

76 

13 

37 

16 

2 

3 

1 

June  21..    .. 

16 

7 

22 

1 

June  22.  .    .  . 

3 

3 

4 

1 

June  25.  . 

1 

June  28.  . 

1 

1 

Totals 

Males  

834 

29 

79 

66 

196 

136 

3 

14 

Females.. 

1683 

17 

23 

134 

145 

106 

3 

11 

1907.]  WHITE-GRUBS  AND  MAY-BEETLES.  465 

Our  data  show  about  thirty  cases  of  oviposition  by  seven  of  our 
species  in  our  breeding-cages,  ranging  in  date  from  the  ist  of  June 
to  the  middle  of  July.*  As  the  beetles  have  begun  to  emerge  more 
than  two  months  earlier,  it  is  likely  that  they  spend  some  time  in 
feeding  before  oviposition  begins.  In  the  Eighteenth  Report  of 
this  office  it  is  said  (p.  118)  that  the  statement  commonly  made  to 
the  effect  that  the  eggs  are  laid  in  a  ball  of  earth  is  clearly  errone- 
ous. This  assertion  must  be  corrected  in  the  light  of  numerous  ex- 
periments made  in  my  insectary  in  1906  with  May-beetles  of  several 
species,  all  of  which  so  deposited  their  eggs  in  the  ground  that  each 
was  found  inclosed  within  an  earthen  ball,  a  half  inch  in  diameter, 
probably  formed  by  the  extrusion  with  the  egg  of  an  adhesive  fluid 
which,  upon  hardening,  held  together  the  particles  of  earth  which  it 
had  penetrated.  This  method  of  inclosure  was  so  general  that  eggs 
were  most  easily  found  by  sifting  the  dirt  in  breedi-ng-cages  and 
breaking  open  the  spherical  pellets  of  earth  thus  separated.  The 
eggs  were  laid  at  depths  varying  from  not  more  than  an  inch  to 
five  or  six  inches  below  the  surface,  the  number  for  each  female 
varying  from  44  for  a  specimen  of  L.  inversa  to  67  for  L.  implicita. 
The  following  extract  from  the  breeding-cage  report  of  Mr.  J. 
J.  Davis  will  give  additional  particulars  of  interest. 

L.  inversa.  June  12,  1906,  I  female  beetle  in  breeding-cage. 
June  1 8,  the  earth  examined  and  44  eggs  found,  each  in  a  ball  of 
earth  from  3  to  3^2  inches  below  the  surface.  Eggs  of  a  pure  milky 
color  and  of  an  oval  shape,  measuring  i  X  X  2  mm.  By  the  end  of 
three  days  they  had  swollen  to  a  nearly  spherical  form,  now  measur- 
ing 2  X  2}4  mm-  Hatching  first  observed  July  n. 

L.  hirticula.  Beetles  collected  and  placed  in  breeding-cage  June 
19,  1906.  No  eggs  were  found  till  July  2,  but  July  9,  6  were  found, 
each  in  its  ball  of  earth.  The  freshest  eggs  were  white  with  a 
glossy  luster.  They  measured  at  first  from  il/2  X  2  mm.  to  2  X  2^2 
mm.  Five  days  later  these  eggs  had  swollen  to  2  mm.  in  diameter, 
and  were  2l/2  to  2^4  mm.  in  length. 

L.  ephelida.  A  single  egg  obtained  August  4,  1905,  from  beetles 
collected  at  Carbondale,  111.,  July  26,  and  placed  in  breeding-cage 
in  insectary  July  29.  This  egg  was  comparatively  small  and  defi- 
nitely oval,  measuring  at  first  IJ/3X2  mm.,  and  later  1^X2  mm. 
L.  ilicis.  From  beetles  collected  June  19,  1906,  eggs  were  found 
in  oval  balls  of  earth  July  9,  none  having  been  present  there  on  the 
2d  of  that  month.  The  eggs  were  a  dull  white,  quite  different  from 
the  glossy  luster  of  those  of  L.  hirticula.  They  measured  at  first 

*A  specimen  of  L.  ephelida,  taken  July  29,  1905,  at  Carbondale,  in  southern  Illinois,  laid 
eggs  until  August  4. 


466 


BULLETIN  No.  116. 


[August, 


i/^  X  2^2   to  23/4   mm.,  the  shorter  diameter  later  enlarging  to 

2  mm. 

L.  crcnulata.  From  a  single  female  beetle  placed  in  a  breeding- 
cage  July  15,  1905,  three  eggs  were  obtained  three  days  later, 
deposited  at  a  depth  of  about  an  inch.  These  eggs  were  oval,  measur- 
ing il/2  to  2l/2  mm.  They  were  white  when  first  laid,  but  changed 
afterwards  to  cream  color. 

L.  fusca.  Eggs  were  obtained  June  22,  1905,  from  beetles  which 
had  been  placed  in  a  breeding-cage  April  24.  One  of  these  eggs 
hatched  on  me  27th  of  June. 

L.  implicita.  Adults  collected  at  Elliott,  111.,  from  cells  in  the 
earth,  were  placed  in  a  breeding-cage  in  the  insectary  October  13, 

1905.  They  were  first  seen  out  of  their  winter  quarters  April  28, 

1906.  June  12,  1906,  3  females  were  alive  and  6  eggs  were  found 
by  sifting  the  dirt.     On  the  2oth  of  June  only  I  beetle  remained 
alive,  and  this  was  a  female.    No  more  eggs  were  found  up  to  June 
25,  but  on  the  5th  of  July  42  eggs  were  sifted  out  of  the  dirt,  each 
in  its  separate  ball  of  earth.    These  were  from  5^  to  6  inches  below 
the  surface.  Those  most  recently  laid,  measured  1 1/4  X  2  to  2^4  mm., 
while  those  which  were  longest  deposited  measured  2  X  2^2  rnm. 

RELATIONS  TO  WEATHER. 

The  beetles  of  Lachno sterna  transform  from  the  pupa  in  summer 
and  fall,  remaining,  as  a  rule,  in  their  underground  cells,  from  2  or 

3  to  5  or  6  inches  below  the  surface,  unaffected,  so  far  as.  we  know, 
by  any  degree  of  cold  to  which  they  are  likely  to  be  subjected  in  our 
climate.     Their  nocturnal  movements  after  they  come  out  of  the 
earth  are,  however,  easily  influenced  by  the  weather.    During  thirty- 
one  nights,  commencing  May  14  and  ending  June  28,  1906,  these 
beetles  were  studied  and  collected  at  Urbana  by  Mr.  West.    On  five 
of  these  nights  no  beetles  were  seen  or  caught,  although  the  fields, 
the  lights,  and  all  the  best  feeding  grounds  were  visited.    The  rec- 
ords of  minimum  temperature  for  these  five  barren  nights,  and  the 
rate  and  direction  of  the  wind,  were  as  follows  : 


Date 

Minimum  Temperature 

Rate  and  Direction  of  Wind 
(Anemometer  Record) 

May  19  

41°  F. 

N.  E.    6  to    8  miles  per  hour 

May  28  

42°  F. 

N.  E.    4  to  14  miles  per  hour 

May  29  

38°  F. 

S.  E.    6  to  12  miles  per  hour 

June  11  

49°  F. 

N.  E.    12  miles,  all  night 

June  12  

46°  F. 

N.  E.    14  miles,  all  night 

1907.]  WHITE-GRUBS  AND  MAY-BEETLES.  467 

No  beetles  were  taken  on  any  night  when  the  thermometer  regis- 
tered below  52°,  except  May  21,  when  the  temperature  was  62°  at 
9  p.  m.  but  fell  to  46°  before  morning.  A  cold  rain  or  high  wind 
kept  them  confined  at  night  to  their  day-time  hiding  places,  and  they 
were  never  abundant  on  their  food  plants,  or  flying  freely,  unless 
the  minimum  temperature  was  at  least  60°.  They  appeared  in  great- 
est numbers  on  warm  quiet  nights  following  bright  sunny  days. 
The  beetles  continue  feeding  during  rain  if  a  storm  comes  up  during 
a  night  favorable  to  their  movements;  and  even  their  flights  are 
not  wholly  suppressed  by  moderate  rain  if  the  weather  is  warm. 

MODES  AND  PLACES  OF  HIBERNATION. 

Our  common  white-grubs  hibernate,  in  the  latitude  of  central 
Illinois,  in  the  two  stages  of  larva  and  beetle,  and  in  these  stages 
only.  In  fifty-seven  collections,  distributed  over  several  years,  ob- 
tained by  following  the  plow  in  fall  and  in  spring,  not  a  single  pupa 
of  these  species  has  occurred,  although  recently  transformed  beetles, 
still  inclosed  in  their  pupal  cells,  have  been  collected  by  the  hundred. 
The  pupa  of  Lachnosterna  may  possibly  go  through  the  winter  now 
and  then,  transforming  the  following  spring,  but  this  is  certainly 
an  extraordinary  occurrence  in  our  latitude,  quite  insignificant  as  a 
factor  in  the  life  history  of  the  species.  It  is  also  a  very  unusual 
thing  for  the  beetles  to  come  out  of  the  ground  in  fall.  Indeed, 
those  taken  from  the  earth  and  placed  in  breeding-cages  in  either 
fall  or  early  spring,  commonly  bury  themselves  without  delay.  Now 
and  then  a  single  specimen  may  be  found  active  in  fall,  but  we  have 
seen  but  one  such  case  in  the  course  of  our  several  years'  work.  The 
beetles  are  evidently  more  resistant  to  cold  than  the  grubs,  and  do 
not  attempt,  as  a  rule,  to  escape  by  going  farther  into  the  ground 
with  the  approach  of  winter. 

During  the  summer  most  of  the  grubs  are  near  the  surface  of 
the  soil.  A  small  percentage  may  be  found  to  a  depth  of  eight  or 
even  ten  inches,  but  the  average  is  about  three  inches.  In  late  fall 
they  begin  to  go  down  as  a  protection  against  the  approaching  win- 
ter's cold,  and  may  reach  a  depth  of  two  to  two  and  a  half  feet.  In 
October  and  November,  1905,  the  downward  movement  of  the 
grubs  infesting  a  field  of  corn,  part  of  which  had  been  completely 
destroyed  by  them,  was  followed  by  digging  over,  on  each  of  five 
days,  several  areas  each  three  and  a  half  feet  square,  and  counting 
the  grubs  exposed.  The  following  table  gives  the  dates  at  which 
this  search  was  made,  the  average  number  of  grubs  found  for  each 
square  of  three  and  a  half  feet,  the  range  in  depth  of  the  grubs  dug 
out,  and  the  average  depth  for  each  date. 


46$ 


BULLETIN  No.  116. 


[August, 


Date 

Average  Grubs 
per  Square 

/Range  in  Depth 

Average  Depth 

Oct.     3,  1905.      . 

29.2 

Near  surface  to    8  in. 

3.5 

Oct.  10,  19U5.      . 

22.6 

Near  surface  to  10  in. 

3.1 

Oct.  23,  1905.      . 

25.3 

Near  surface  to  10  in. 

3.1 

Oct.  31,  1905.      . 

22. 

Near  surface  to  16  in. 

6.4 

Nov.  22,  1905.      . 

24.75 

Three  in.  to  23  in. 

10. 

November  22,  the  last  of  the  above  dates,  most  of  these  grubs 
were  from  7  to  14  inches  below  the  surface;  but  one  was  found  only 
3  inches  down,  seven  had  stopped  at  a  depth  of  about  6  inches,  and 
three  had  gone  to  20  to  23  inches  below  the  surface.  The  ground 
did  not  freeze  permanently  until  several  days  after  this  date. 

The  grubs  approach  the  surface  in  spring  when  the  frost  leaves 
the  ground  and  the  soil  becomes  fit  to  plow,  and  one  often  sees  in 
the  bottom  of  the  furrow  the  tubular  burrows  made  by  them  in 
coming  up  from  their  winter  quarters. 

PRINCIPAL  ENEMIES. 

"  Swine. — Pigs  are  by  far  the  most  destructive  enemies  of  white- 
grubs  and  of  May-beetles.  They  are  extremely  fond  of  these  insects, 
and  of  all  others  within  their  reach  which  are  large  enough  to  at- 
tract their  attention,  and  the  diligence  with  which  they  will  tear  in 
pieces  the  sod  of  an  infested  pasture,  and  the  depth  to  which  they 
will  dig  in  pursuit  of  grubs  in  cultivated  ground  are  matters  of 
common  observation.  They  will  also  search  out  and  destroy  the 
May-beetles  in  May  and  June  if  allowed  to  range  over  pastures  and 
meadows  where  these  insects  hide  by  day  and  to  which  they  resort 
to  lay  their  eggs.  Pigs  are  consequently  our  most  useful  agents  for 
the  destruction  of  these  insects — a  point  which  will  be  more  fully 
discussed  in  this  paper  under  "Measures  of  Prevention  and  Rem- 
edy." 

Crows  and  Blackbirds. — Next  to  pigs  the  most  efficient  destroy- 
ers of  white-grubs  among  our  common  larger  animals  are  crows 
and  crow-blackbirds,  both  of  which  eat  them  greedily  where  they 
can  find  them  in  sufficient  numbers  to  make  them  an  important  ar- 
ticle of  food.  Evidence  on  this  point  is  less  positive  with  respect  to 
crows  than  concerning  blackbirds.  Mr.  W.  B.  Burrows,  of  the  U.  S. 
Department  of  Agriculture,  who  has  studied  the  food  of  the  com- 
mon American  crow  by  examining  the  contents  of  more  than  a 
thousand  stomachs,  reports  that  he  has  found  white-grubs  in  a  com- 
paratively small  number  of  these  stomachs,  but  that  May-beetles  had 
been  eaten  by  very  nearly  all  the  crows  taken  at  a  time  when  these 


1W7.]  WHITE-GRUBS  AND  MAY -BEETLES.  469 

insects  were  abundant  in  the  beetle  stage,  making,  indeed,  the  greater 
part  of  the  insect  food  of  all  the  crows  collected  at  that  time. 

To  these  well-known  facts  I  have  to  add  two  significant  items  of 
observation  reported  to  me  by  my  field  assistants.  One  of  these, 
Mr.  E.  O.  G.  Kelly,  who  was  engaged  during  much  of  the  season 
of  1906  in  a  field  study  of  injuries  by  white-grubs,  unusually  serious 
that  year  in  central  Illinois,  tells  me  that  he  often  saw  considerable 
numbers  of  crows  following  after  the  plow  in  fall,  evidently  picking 
up  white-grubs,  and  that  he  has  also  seen  flocks  9$  crows  alight  in 
a  badly  infested  pasture  and  tear  the  sod  in  pieces  in  search  of  the 
grubs,  fighting  with  each  other  for  their  possession  when  thus  ex- 
posed. Another  assistant,  Mr.  A.  O.  Gross,  employed  last  fall  in 
collecting  data  for  a  census  of  the  bird  life  of  Illinois,  found,  in  a 
trip  across  the  state  made  on  foot  in  September  and  October,  that 
next  to  the  horned  lark,  crows  were  the  most  abundant  birds  on 
plowed  ground,  averaging  seventy-nine  per  square  mile  in  all  the 
recently  plowed  fields  crossed  on  that  trip.  They  could  have  had  no 
other  object  there  than  the  search  for  insect  food.* 

In  a  study  of  the  food  of  blackbirds,  made  by  Mr.  F.  E.  L.  Beal 
for  the  U.  S.  Department  of  Agriculture  in  1894,  it  was  found  that 
these  birds  ate  either  beetles  or  grubs  in  every  month  from  March 
to  October  inclusive.  In  May  these  insects  made  more  than  a  sixth, 
and  in  June  one  ninth,  of  the  entire  food.  Many  stomachs  were 
found  to  be  literally  crammed  with  grubs ;  and  in  many  more,  grubs 
had  formed  a  large  part  of  the  previous  meal. 

The  Common  Grub  Wasp  (Tiphia}. — Much  the  most  important 
insect  enemy  of  the  white-grubs  is  a  wasplike  insect  belonging  to  the 
hymenopterous  genus  Tiphia.  It  is  a  slender,  jet-black  species,  usu- 
ally about  two  thirds  of  an  inch  long,  but  sometimes  smaller,  and 
with  wings  either  clear  or  more  or  less  deeply  tinged  with  dusky 
yellow.  It  enters  the  ground  in  search  of  the  grubs,  follows  them 
up  in  their  burrows,  and  lays  on  the  back  of  each  grub  a  single  egg, 
which  hatches  in  a  little  over  a  week  into  a  footless,  maggot-like 
larva.  This  larva  adheres  to  the  surface  of  the  insect,  punctures  its 
skin  and  sucks  its  blood  for  a  time,  but  finally  eats  it  up.  The  Tiphia 
larva  then  spins,  under  ground,  an  oval  brown  coccoon  within  which 
it  goes  through  its  transformations,  coming  out  as  a  winged  insect 
the  following  summer.  The  rate  of  multiplication  of  the  species 
is  not  known,  but  it  is  certainly  sufficient  to  enable  the  Tiphia  vir- 
tually to  destroy,  under  favorable  circumstances,  the  entire  grub 
population  of  a  badly  infested  field. 

*" An  Ornithological  Cross-section  of  Illinois  in  Autumn.''  By  S.  A.  Forbes.     Bull.  111. 
State  Lab.  Nat.  Hist.,  Vol.  VII.,  Art.  IX.,  p.  318. 


470  BULLETIN  No.  116.  [Auyust, 

The  method  of  the  operations  of  this  insect  and  the  main  facts 
of  .its  life  history  have  been  worked  out  in  my  insectary  during  the 
past  two  years  by  Mr.  J.  J.  Davis  and  Mr.  J.  A.  West  from  coccoons 
and  infested  grubs  sent  in  by  Mr.  Kelly  from  fields  at  Elliott,  111. 
Thirty-three  Tiphia  cocoons  were  used  in  these  observations,  twenty- 
one  of  which  were  obtained  November  25,  1905,  and  twelve  April 
27,  1906.  From  those  collected  .in  fall  the  winged  insect  emerged 
at  thirteen  dates  between  June  19  and  July  28,  1906,  and  those  ob- 
tained in  spring  yielded  the  adult  on  eleven  dates  between  June  26 
and  August  22.  These  collections  consequently  do  not  represent  dif- 
ferent broods.  -  Only  seven  of  the  adults  obtained  were  males,  and 
twenty-five  were  females,  the  sex  of  one  being  undetermined. 

A  pair  were  seen  in  copula  in  one  of  the  breeding-cages  at  9 130 
p.  m.  July  i,  and  eggs  were  laid  on  grubs  in  the  insectary  from  June 
29  to  August  21.  One  lot  of  young  white-grubs  brought  in  Sep- 
tember 20,  1906,  were  already  badly  infested  by  very  small  Tiphia 
larvae  about  one  eighth  of  an  inch  in  length.  As  insectary  observa- 
tions show  that  the  eggs  hatch  in  from  seven  to  ten  days,  and  that 
the  young  larva  reaches  the  length  of  an  eighth  of  an  inch  in  about  a 
week,  it  appears  that  the  eggs  for  these  larvae  were  laid  a  little  later 
than  September  i.  The  period  of  oviposition  of  this  grub  wasp  is 
thus  something  more  than  two  months. 

In  several  cases  a  female  Tiphia  was  induced  to  go  through  the 
whole  operation  of  preparing  her  victim  and  depositing  her  egg 
upon  it  above  ground  in  a  breeding-cage,  where  she  could  be  con- 
tinuously watched,  and  the  facts  thus  learned  are  unusually  inter- 
esting. Like  others  of  its  family — the  digger-wasps,  or  Scoliidce — 
these  insects  sting  their  prey  before  attaching  the  egg  to  it,  with  the 
effect  to  paralyze  it  more  or  less  completely.  Mounting  the  body  of 
the  grub,  which  struggles  violently  against  the  attack,  the  Tiphia 
seizes  with  her  mandibles  the  skin- of  the  back  just  behind  the  head, 
curving  her  body  downward  around  the  side  of  the  grub,  with  the  tip 
of  her  abdomen  beneath  and  just  behind  the  head,  and  then,  after  feel- 
ing about  with  the  abdomen  for  a  time,  finally  stings  her  victim,  with 
the  effect  suddenly  to  quiet  its  struggles  and  reduce  it  to  helpless- 
ness. Then  the  Tiphia  reverses  her  position  and  works  the  tip  of  her 
abdomen  backward  and  forward  for  several  minutes  in  one  of  the 
grooves  or  creases  on  the  back  of  the  larva,  usually  not  far  behind  the 
head,  apparently  smearing  the  surface  there  with  a  viscid  fluid,  after 
which  she  deposits  her  egg  on  this  sticky  surface  and  goes  away.* 

*The  above  account  is  based  on  insectary  observations  and  experiments.  Several  white- 
grubs  parasitized  by  Tiphia  larva  have  been  found  in  the  field  since  this  was  written,  and  in 
every  case  the  larva  was  on  the  under  side  of  the  body  between  the  thoracic  leg's. 


1907.]  WHITE-GRUBS  AND  MAY-BEETLES.  471 

The  larva,  at  first  almost  completely  paralyzed  by  the  puncture 
of  the  sting  and  the  venom  doubtless  injected  at  the  same  time, 
slowly  revives,  recovering  presently  its  full  powers  of  locomotion, 
so  that  it  is  indistinguishable  by  its  behavior  from  its  fellows  which 
have  not  been  stung.  The  stinging,  in  this  case,  is  thus  a  means  of 
quieting  the  struggles  of  the  grub  in  a  way  to  permit  the.  Tiphia  to 
attach  her  egg  to  its  back.  Commonly,  of  course,  these  operations 
go  on  under  ground.  A  Tiphia  introduced  into  a  breeding-cage  con- 
taining grubs  in  the  earth  disappears  under  ground  herself,  and  does 
not  come  out  until  she  has  found  and  infested  a  grub. 

Repeatedly,  where  grubs  were  exposed  to  attack  on  the  surface 
of  the  dirt  in  breeding-cages,  the  Tiphia  merely  stung  them  at  first, 
and  then  proceeded  to  bury  them  before  depositing  her  egg.  For 
this  purpose,  she  undermined  the  grub  by  digging  the  earth  from 
beneath  it,  pulling  its  body  about  by  means  of  her  jaws  until  it  was 
in  proper  position  to  enter  the  hole,  gradually  digging  deeper,  and 
finally  burying  it  completely.  In  one  case  in  which  the  operation 
was  timed,  the  grub  was  buried  in  ten  minutes  after  it  was  stung. 
Sometimes  the  Tiphia  abandoned  an  attempt  at  burial,  and  left  the 
grub  without  placing  an  egg  on  it  after  it  was  stung. 

Apart  from  that  general  exhibition  of  a  wonderful  adaptation 
of  its  actions  to  the  needs  of  its  prospective  progeny  which  this  Ti- 
phia shares  with  many  other  wasps,  and  especially  with  those  of  its 
own  family,  there  are  two  points  of  peculiar  interest  in  this  account 
It  is  an  unmistakable  fact  that  the  effect  of  the  poisoning  of  the 
grubs  by  the  Tiphia  is  merely  to  paralyze  the  victim  temporarily ;  to 
overcome  its  resistance  and  reduce  it  to  helplessness  while  the  Tiphia 
egg  is  being  placed  in  position.  The  sting  is  used  as  a  mere  aid  in 
the  struggle  of  the  Tiphia  with  a  stronger  insect.  This  fact  may 
point  to  the  explanation  of  the  origin  of  the  remarkable  instinct  of 
the  solitary  wasps  to  sting  and  paralyze  their  prey. 

More  remarkable  still,  however,  in  the  light  of  our  present 
knowledge  of  the  habits  of  Tiphia,  is  its  frequent  burial  of  white- 
grubs  exposed  to  it  on  the  surface  of  the  ground.  Since  digger- 
wasps  in  general  are  parasites  of  underground  larvae  only,  since  the 
Tiphia  is  not  known  to  infest  any  insects  except  white-grubs  of  the 
genus  Lachnosterna,  and  since  in  nature  it  can  never  find  these 
grubs  above  ground, 'its  deliberate  burial  of  exposed  grubs  has  all 
the  appearance  of  a  line  of  action  extemporized  to  meet  a  previously 
unknown  condition.  Either  the  Tiphia,  disturbed  at  finding  its  prey 
exposed,  buries  this  as  a  result  of  impulse  aided  by  intelligent  con- 
trivance, or  we  shall  find,  when  its  habits  are  known  in  full,  that  it 


472  BULLETIN  No.  116.  [August, 

does  sometimes  normally  infest  and  attack  insects  exposed  above 
ground  by  their  habits,  burying  them  as  a  matter  of  instinct  after 
it  has  placed  its  egg.  Tiphia  has  not,  in  fact,  been  studied  as  an  in- 
dependent species,  but  all  the  data  concerning  its  habits  and  life 
history  have  been  gathered  in  the  course  of  studies  of  the  white- 
grubs. 

The  egg  of  Tiphia  remains  firmly  glued  to  the  back  of  the  chosen 
grub,  and  hatches  in  seven  to  ten  days.  The  young  larva  breaks  its 
way  out  from  the  egg  at  one  end,  and,  although  it  begins  at  once  to 
feed,  it  does  not  at  first  free  itself  from  the  shell,  but  as  it  grows 
this  finally  splits  and  breaks  away.  When  it  first  emerges  the  larva 
measures  slightly  more  than  a  millimeter  in  length.  From  our  scanty 
data  it  appears  that  it  takes  about  two  weeks  to  get  its  full  growth, 
and  that  it  doubles  its  size  in  the  last  two  days  of  its  larval  life,  dur- 
ing which  it  is  engaged  in  devouring  the  body  of  its  host.  Previous 
to  this  time  it  has  been  adherent  to  the  skin  of  the  grub  whose  fluids 
it  has  lived  upon.  When  full  grown  it  is  from  two  thirds  to  four 
fifths  of  an  inch  in  length. 

The  cocoons  are  cylindrical  ovate,  from  17-22  mm.  long,  clay- 
colored  at  first,  and  wood-brown  or  cinnamon-brown  when  older. 
From  our  observations  thus  far  made  it  appears  that  the  larva 
hibernates  within  the  cocoon,  not  pupating  until  the  following 
spring.  The  adult  emerges  from  a  little  one  side  of  the  larger  end, 
in  which  it  leaves  a  ragged  and  irregular  opening.  In  several  cases 
the  abundance  of  these  conspicuous  brown  cocoons  in  the  earth  was 
such  as  to  indicate  an  enormous  destruction  of  white-grubs,  and 
there  is  no  doubt  that  this  parasite  is  an  important  agent  in  checking 
destructive  uprisings  of  these  insects. 

That  this  wasp,  parasitic  on  white-grubs,  is  itself  parasitized,  is 
shown  by  the  results  of  observations  made  on  Tiphia  cocoons  col- 
lected April  27,  1906,  and  kept  in  breeding-cages  during  the  sum- 
mer. From  these  emerged,  July  7,  16,  and  31,  adult  bee-flies  (Bom- 
byliidce)  of  the  species  Exoprosopa  fascipennis,  each  freeing  itself 
from  the  Tiphia  cocoon  by  cutting  out  a  circular  piece  at  the  larger 
end.  The  eggs  from  which  these  flies  resulted  were  probably  laid 
on  the  Tiphia  grub  in  1905,  before  the  cocoon  was  spun. 

MISCELLANEOUS  INSECT  ENEMIES. 

Macrophthalma  disjuncta. — This  little  tachinid  fly  was  men- 
tioned in  my  Seventh  Report  as  bred  repeatedly  from  dead  white- 
grubs,  but  I  was  nevertheless  uncertain  that  it  was  a  parasite.  Lately 
its  parasitic  nature  has  been  proven  by  repeatedly  breeding  it  from 


1907.]  WHITE-GRUBS  AND  MAY- BEETLES.  473 

living  grubs  kept  in  breeding-cages  in  my  insectary.  Adults  have 
emerged  in  these  experiments  March  26,  June  8,  July  12,  and  Au- 
gust 8,  and  others  have  been  taken  at  electric  lights  July  9,  and  in  a 
corn  field  September  27.  Those  appearing  March  26  lived  in  con- 
finement until  May  14.  We  have  thus  seen  these  insects  alive  in 
every  month  from  March  to  September  inclusive.  In  the  breeding- 
cages,  remains  of  a  white-grub  were  commonly  found  "associated 
with  the  cocoon  of  the  parasite. 

The  adult  of  this  species  is  a  large  blackish-gray  fly  with  a  gen- 
eral resemblance  to  the  common  large  blow-fly,  but  with  a  grayish 
white  sheen  on  the  basal  half  of  each  segment  of  the  abdomen,  giv- 
ing the  effect  of  equal  alternating  cross-bands  of  black  and  gray. 

Ophion  bifoveolatum  Brulle. — This  well-known  parasite  of  the 
white-grub  has  been  reared  by  us  several  times  from  these  insects. 
In  one  case  the  head  and  skin  of  a  grub  were  woven  into  the  wall  of 
the  cocoon  of  the  parasite.  The  species  has  been  bred  by  us  repeat- 
edly from  cocoons  collected  from  the  latter  part  of  July  to  the  first 
of  September,  and  kept  in  breeding-cages  through  the  winter,  adults 
appearing  from  March  3 1  to  April  27. 

The  adult  is  a  large,  slender-bodied,  dark  red  ichneumon-fly; 
and  the  cocoon  is  quite  regularly  elliptical,  a  half  inch  long  by  a 
fourth  of  an  inch  thick  at  the  middle,  smooth,  dull  brownish,  or 
more  or  less  blackish — especially  towards  the  end. 

Sparnopolius  fulvus  Wied. — This  bee-fly,  which  we  have  some- 
times noticed  in  corn  fields  and  have  collected  from  miscellaneous 
sweepings  of  vegetation  in  midsummer,  also  proves  to  be  a  parasite 
of  the  white-grub,  as  shown  by  breeding-cage  work  done  in  1904 — 
1906.  It  was  first  detected  in  this  relation  by  Mr.  E.  P.  -Taylor,  of 
my  office,  who  found  a  white-grub  at  Elliott,  111.,  August  25,  1904, 
with  a  dipterous  larva  attached  to  its  back.  This  was  placed  in  an 
insectary  cage,  which  was  not  examined  until  April  21,  at  which 
time  the  white-grub  -had  been  completely  destroyed,  and  the  larva 
had  completed  its  transformations.  It  probably  had  emerged  in  the 
fall  of  1904.  A  larva  of  this  same  species  was  next  collected  July 
24,  1906,  from  among  corn  roots  at  Effingham,  111.,  and  was  placed 
in  a  breeding-cage  to  obtain  the  adult.  It  pupated  August  22,  and 
emerged  as  a  winged  insect  September  10.  All  our  open-air  collec- 
tions of  this  fly  have  been  obtained  in  August. 

The  adult  is  about  as  large  as  a  common  house-fly,  but  is  covered 
with  erect  yellow  fur.  The  pupa  is  not  inclosed  in  the  last  larval 
skin.  Its  head  bears  three  large  points  on  each  side  anteriorly,  and 
a  smaller  pair  beneath  at  the  base  of  the  mouth-parts.  The  last  seg- 


474  BULLETIN  No.  116.  [August, 

ment  of  the  pupa  is  rather  narrowly  truncate,  with  a  small  slender 
spine  on  each  side  of  the  truncation,  and  a  shorter  one  beneath  each 
of  these. 

Considerable  numbers  of  another  species  of  parasitic  larva  were 
taken  by  Mr.  Kelly  at  Elliott,  111.,  August  29  and  September  20, 

1906.  These  were  evidently  white-grub  parasites,  as  the  remains  of 
the  grubs'were  still  clinging  to  several  of  them.    This  species  is  still 
in  the  larval  stage  at  this  writing. 

Three  yellow  coarcate  meloid  larvae  were  also  found  by  the  same 
assistant  in  an  infested  oats  field  with  the  remnants  of  white-grubs 
attached  to  them,  and  another  was  taken  in  a  similar  condition  Oc- 
tober 10.  These  specimens  have  not  yet  matured. 

Pyrgota  undata  Wied. — One  of  the  most  interesting  parasitic 
enemies  of  the  white-grubs  is  a  large,  rather  unusual-looking  fly  of 
the  family  Ortalidce,  noticed  by,  Mr.  J.  A.  West,  an  assistant  of  my 
office,  as  abundant  among  the  beetles  at  night.  Now  and  then  May- 
beetles  were  seen  to  drop  to  the  earth,  trying  to  rid  themselves  of  the 
adult  flies  which  were  clinging  to  their  backs,  each  with  the  last 
segment  of  the  abdomen  thrust  in  between  the  wings  and  wing- 
covers  of  the  beetle  and  firmly  held  in  place  over  the  middle  of  the 
abdomen.  The  flies  were  apparently  thus  thrusting  their  eggs  into 
the  backs  of  the  beetles  through  the  thin  dorsal  skin  beneath  the 
wing-covers.  The  tip  of  the  abdomen  of  the  female  fly  is  admirably 
adapted  to  this  object,  being  hard  and  subconical,  and  directed  down- 
wards at  a  right  angle  to  the  axis  of  the  body. 

The  relations  of  these  insects  were  experimentally  determined 
by  confining,  June  9,  1906,  adult  May-beetles  in  a  breeding-cage 
with  several  of  the  flies.  These  would  light  on  the  backs  of  the 
feeding  beetles,  which  would  at  once  drop  to  the  ground  with  the 
flies  clinging  to  them.  Whenever  a  beetle  spread  its  wings  for  flight 
the  insect  on  its  back  inserted  the  tip  of  its  abdomen  between  the 
May-beetle's  wings,  evidently  depositing  an  egg  in  its  back.  Beetles 
so  treated  lived  for  some  days,  and  then  began  to  die.  On  the  2/th 
of  June,  five  of  the  beetles  were  dead,  and  in  the  bodies  of  two  of 
these,  dipterous  maggots  were  found.  July  10,  three  of  the  beetles 
contained  each  a  dipterous  puparium,  which  remained  unchanged 
until  May  of  this  year,  when  all  produced  adults  of  P.  undata.  Au- 
gust 29  and  September  20,  1906,  several  puparia  were  found  in  the 
bodies  of  dead  May-beetles,  and  these,  kept  in  breeding-cages 
through  the  winter,  produced  adults  of  P.  undata  May  14  and  17, 

1907.  Like  experiments  begun  during  the  present  year  have  pro- 
gressed similarly  to  the  time  of  writing.    Adult  flies  of  this  species 


1907.]  WHITE-GRUBS  AND  MAY-BEETLES.  475 

were  again  frequently  seen  June  12  to  18,  1907,  among  May-beetles 
on  trees  at  night,  no  less  than  twenty-six  specimens  being  captured. 
These  flies  have  also  been  occasionally  taken  at  electric  lights,  and 
in  various  situations  by  day  during  different  years,  from  May  20 
to  June  17. 

The  puparia  of  these  parasites  are  dull  black,  broad  ovate,  widest 
at  the  posterior  third.  At  the  tip  is  a  small  shallow  excavation  en- 
circled by  a  rugose  ridge,  which  is  elevated  latero-dorsally  into  a 
pair  of  short  irregular  tubercles,  the  tips  of  which  are  about  a  milli- 
meter apart.  Length  7-8  mm. ;  greatest  diameter,  4.5-4.8  mm. ; 
diameter  of  anterior  end,  about  3  mm.  The  adult  flies  are  yellow- 
brown,  three  eighths  to  half  an  inch  long.  The  head  is  subtriangular, 
the  thorax  globose,  the  abdomen  slender  at  base,  enlarging  apically. 
The  wings  are  three  eighths  to  half  an  inch  long,  conspicuously  and 
characteristically  marked.  The  entire  anterior  margin  of  the  wings 
has  a  broad  brown  border  reaching  half  way  across  the  wing,  and 
having  two  broad  saw-tooth-like  extensions  attaining  the  posterior 
margin,  one  at  the  middle  of  the  apical  half  and  the  other  at  that 
of  the  basal  half.  The  first  two  abdominal  segments  are  about  as 
long  as  broad,  and  connate;  the  next  four,  in  the  female,  are  very 
short,  followed  by  the  genital  segment,  which  is  very  large,  shining, 
directed  downwards  and  curved  slightly  forwards. 

The  male  abdomen  is  similarly  shaped :  the  two  basal  segments 
are  followed  by  two  more  about  twice  as  long  as  the  corresponding 
ones  in  the  female ;  the  next  segment  is  a  little  longer  than  broad, 
vertically  directed,  bearing  the  genital  segment,  which  is  directed 
somewhat  anteriorly.  The  eyes  are  larger  in  the  female  than  in 
the  male. 

Other  Dipterous  Parasites. — In  1905  a  May-beetle  of  the  species 
Lachno sterna  crenulata  found  near  Urbana  July  15,  laid  three  eggs, 
and  died  about  the  29th  of  July.  On  August  5  an  adult  tachinid 
emerged  from  the  body  which  Mr.  Tyler  Townsend,  of  the  U.  S. 
National  Museum,  regards  as  a  new  species — Viviana.  Two  dip- 
terous larvae  were  found  June  27,  1906,  in  a  May-beetle  taken  alive 
May  31.  July  10  these  larvae  had  formed  puparia,  and  adult  tachinid 
flies  emerged  May  17  and  18  of  the  following  year.  These  are 
slightly  larger  than  a  house-fly,  with  black  subquadrate  thorax,  the 
anterior  angles  each  with  a  triangular  red  spot.  The  puparium  is 
very  dark  red,  almost  black,  subcylindrical,  with  rounded  ends. 
Length,  7  mm. ;  width,  3  mm.  It  is  smoothly  rounded  behind,  with 
a  pair  of  low  tubercles  placed  close  together.  The  species  has  not 
been  determined. 


476  BULLETIN  No.  116.  [August, 

RELATION  TO  SOIL  AND  SUBSOIL. 

It  is  a  matter  of  common  opinion  that  injuries  by  white-grubs 
are  more  serious  on  the  higher,  lighter,  and  drier  parts  of  our  culti- 
vated areas  than  on  the  lower  and  moister  parts,  but  no  exact  ob- 
sevations  have  been  made  to  show  whether  this  apparent  difference 
is  real  under  all  conditions,  and  whether,  if  so,  it  is  due  to  a  greater 
abundance  of  the  grubs  on  high  lands  than  on  low,  or  to  a  lesser 
average  power  of  recuperation  and  resistance  on  the  part  of  plants 
growing  in  comparatively  light  and  less  fertile  soils. 

I  began  in  1904  and  1905  to  accumulate  data  on  this  and  allied 
points,  by  having  collections  of  white-grubs  made  by  persons  follow- 
ing the  plow,  who  recorded  for  each  field  and  situation  the  number 
of  grubs  found  in  each  quarter  of  a  mile  of  furrow.  A  record  was 
also  made,  for  each  field  examined,  of  the  succession  of  crops  it  had 
borne  for  the  five  years  preceding,  of  the  character  of  the  soil,  the 
lay  of  the  land,  the  conditions  as  to  drainage  and  to  fertilization, 
and  the  relation  of  the  field  to  trees  and  shrubs  on  which  the  parent 
beetles  of  the  grubs  might  have  found  food.  Collections  were  made 
on  this  plan  from  seventy-nine  fields  in  the  following  twelve  counties 
of  central  and  southern  Illinois:  Stark,  Peoria,  Woodford,  Mc- 
Lean, Champaign,  Macon,  Macoupin,  St.  Clair,  Washington,  Ma- 
rion, Jackson,  and  Union.  This  work  was  interrupted  by  lack  of 
funds  and  by  diversion  of  assistants  to  more  pressing  problems 
before  any  sufficient  mass  of  data  had  been  obtained  to  enable  me 
to  draw  satisfactory  general  conclusions  on  any  one  of  the  points  of 
principal  interest.  So  far  as  they  go,  they  show  that  the  grubs  were 
more  abundant  on  the  higher  and  drier  parts  of  the  country  than  on 
the  lower  and  moister  parts,  and  that  the  fewest  eggs  were  laid  by 
the  parent  beetles  in  corn  fields  and  the  most  in  grass-lands.  Thirty- 
eight  low-land  fields  gave  an  average  of  21  grubs  exposed  in  a  mile 
of  plowed  furrow,  and  41  of  the  high-land  fields  an  average  of  31  to 
the  mile.  The  three  largest  numbers  found  in  any  fields  were  208, 
164,  and  140  grubs  to  the  mile,  all  on  high  ground.  The  largest  num- 
bers in  any  of  the  low-land  fields  were  112  and  104  in  two  of  them. 
Again,  the  average  of  fields  which  had  been  in  corn  continuously  for 
at  least  three  years  preceding  was  17  grubs  exposed  in  each  mile  of 
furrow,  and  that  of  fields  which,  although  in  corn  at  the  time,  had 
been  in  grass  for  several  years  preceding,  was  37  grubs  to  the  mile. 
It  is  evident  that  useful  information  may  be  obtained  from  data  of 
this  description  if  they  are  accumulated  in  sufficient  number  and  are 
properly  classified. 


1907.1  WHITE-GRUBS  AND  MAY-BEETLES.  477 

RELATIONS  TO  AGRICULTURAL  MANAGEMENT. 

Injuries  by  white-grubs  are  influenced  to  a  considerable  extent 
by  the  system  of  farming,  and  especially  by  the  succession  of  crops ; 
by  the  management  of  pasture-lands,  in  which,  if  left  wholly  to 
themselves,  they  are  likely  to  accumulate  in  increasing  numbers  year 
by  year ;  and  possibly,  also,  by  the  time  of  the  year  when  infested 
lands  are  plowed.  While  the  old  idea  that  white-grubs  are  essen- 
tially insects  of  pastures  and  meadows  has  been  exploded  by  ob- 
servations of  recent  years,  it  still  remains  true  that,  other  things 
being  equal,  they  are  most  abundant  in  grass-lands,  and  consequently 
most  injurious  to  other  crops  if  these  follow  within  one  or  two 
years  upon  an  infested  pasture  or  meadow.  They  seem  particularly 
liable  to  accumulate  in  an  old  turf  which  has  lain  unbroken  for  sev- 
eral years,  and  are  less  likely  to  be  destructive  where  there  is  a  quick 
rotation  of  crops,  including  a  short  period  in  grass,  to  be  followed 
by  one  or  two  years  in  clover.  The  modern  stockman's  practice  of 
herding  cattle  and  pigs  together  is  an  excellent  one  from  our  stand- 
point, since  the'pigs,  in  following  the  cattle,  are  likely  also  to  search 
out  the  grubs  in  the  turf  and  to  keep  the  sod  practically  free  from 
them. 

It  is  a  matter  of  common,  though  not  universal,  opinion  among 
farmers  who  have  watched  the  work  of  the  white-grubs  that  fall 
plowing  of  infested  lands  is  preferable  to  spring  plowing.  In  the 
absence  of  any  apparent  reason  why  this  should  be  so,  and  in  the 
absence  also  of  any  experiments  upon  the  subject  and  of  any  consid- 
erable number  of  exact  observations,  this  supposition  must  be  re- 
garded as  doubtful.  Our  own  field  reports  give  thus  far  but  a  single 
instance,  reported  by  Mr.  Kelly  in  1905,  of  a  notable  difference  in 
white-grub  injury  corresponding  to  a  difference  in  the  time  of  plow- 
ing of  different  parts  of  the  same  field ;  and  this  instance  is  by  no 
means  clear,  since  there  was  injury  by  grubs  in  both  parts  of  this 
field — much  greater  and  more  extensive,  however,  on  the  spring 
plowing.  The  white-grubs  were  also  reported  as  less  abundant  in 
the  part  of  the  field  plowed  in  fall,  averaging  there  one  grub  to  the 
hill  of  corn  as  compared  with  seven  to  the  hill  found  in  the  part 
plowed  in  spring.  The  data  of  this  observation  are  incomplete,  how- 
ever, and  this  difference  in  number  of  grubs  may  have  been  due  to 
something  else  than  difference  in  the  time  of  plowing. 

INJURIES  TO  CROPS. 

Injuries  to  crops  by  white-grubs  and  May-beetles  are  often  of  the 
most  serious  and  extensive  character.  The  beetles  by  their  destruc- 


478  BULLETIN  No.  116.  [August, 

tion  of  leaves  of  trees  and  shrubs  in  spring  not  infrequently  cause 
the  death  of  those  preferred  by  them  for  food,  and  the  grubs  are 
particularly  destructive  in  towns  to  the  turf  of  lawns,  in  nurseries  to 
young  evergreens,  in  the  fruit  plantations  to  strawberry  vines,  and 
on  the  general  farm  to  grass  and  corn. 

The  injury  by  grubs  is  due,  in  all  cases,  to  the  destruction  of  the 
roots  of  the  plants  infested  and  the  consequent  weakening  or  actual 
killing  of  the  plant.  The  nature  and  extent  of  the  injury  to  corn  is 
well  illustrated  by  observations  made  by  one  of  my  assistants,  Mr. 
Kelly,  in  a  field  near  Ludlow,  in  Champaign  county,  about  ten  acres 
of  which  were  almost  completely  destroyed.  By  digging  up  to  a 
depth  of  twenty  inches,  and  searching  all  the  soil  belonging  to  each 
of  sixty  hills  of  corn — an  area,  that  is,  three  and  a  half  feet  square 
for  each  hill — it  was  found  that  this  badly  injured  area  contained 
an  average  of  3,460  grubs  to  the  hundred  hills,  or  more  than  34  to 
the  hill,1 — a  total  of  about  three  hundred  pounds  of  grubs  to  the  acre 
of  corn.  The  plants  varied  in  height  from  two  inches  to  six  feet, 
and  the  total  number  of  ears  borne  by  two  thousand  hills  was  786, 
all  small  ears  or  nubbins. 

PREVENTION  AND  REMEDY. 

The  subject  of  preventive  and  remedial  measures  was  somewhat 
fully  treated  in  my  Seventh  Report  (pp.  127-137),  and  there  is 
nothing  important  to  add  to  that  discussion  at  the  present  time  be- 
yond a  statement  of  the  results  of  an  experiment  with  pigs  as  a 
means  of  clearing  the  grubs  out  of  an  infested  field.  This  experi- 
ment was  made  in  the  field  above  referred  to,  near  Ludlow,  111.,  ten 
acres  of  the  worst  injured  part  being  surrounded  with  a  temporary 
fence,  and  one  hundred  pigs  averaging  seventy-five  pounds  each, 
together  with  eight  large  sows,  being  turned  into  the  inclosure  Sep- 
tember 23. 

By  October  13  the  pigs  had  rooted  over  the  whole  surface  of 
the  ten-acre  lot,  going,  in  some  places,  to  a  depth  of  ten  or  twelve 
inches.  An  area  equivalent  to  twenty  corn  hills  was  now  examined 
to  a  depth  of  twenty  inches,  with  the  result  that  an  average  of  4.8 
grubs  per  hill  were  found,  as  compared  with  34.6  per  hill  at  the 
beginning  of  the  experiment — a  benefit  of  86  per  cent,  in  twenty 
days.  The  grubs  found  in  the  field  at  this  time  were  usually  eight 
inches  or  more  below  the  surface. 

The  pigs  were  in  this  inclosure  until  October  20,  when  they  were 
removed  to  another  badly  injured  part  of  the  field,  and  a  final  ex- 
amination of  the  plot  was  made.  In  an  area  equal  to  ten  hills  of 


1907.}  WHITE-GRUBS  AND  MAY-BEETLES.  479 

corn  only  two  grubs  were  found — a  benefit  of  over  99  per  cent,  de- 
stroyed by  the  pigs  in  twenty-seven  days.  As  the  grubs  were  at  this 
season  going  down  to  escape  frost,  the  hogs  were  burrowing  in 
pursuit  of  them,  sometimes  to  a  depth  of  two  feet. 

Although  these  pigs  remained  perfectly  thrifty,  it  is  proper  to 
say  that  there  is  one  possibly  serious  objection  to  this  very  common 
use  of  swine  as  a  means  of  keeping  in  check  the  white-grub;  in  grass- 
land and  of  clearing  them  out  of  fields  of  corn.  It  has  been  shown 
by  Dr.  C.  W.  Stiles,  of  the  U.  S.  Bureau  of  Animal  Industry,*  that 
one  of  the  most  injurious  intestinal  parasites  of  swine,  known  as 
the  giant  thorn-headed  worm  (Echinorhynchus  gigas),  passes  one 
stage  of  its  life  in  certain  of  the  white-grubs,  and  that  pigs  become 
infested  by  it  by  devouring  infested  grubs,  which  themselves  obtain 
it  by  way  of  the  excrement  of  the  pigs.  Where  either  grubs  or  pigs 
become  infested  by  these  parasites  the  situation  is  more  or  less  dan- 
gerous if  pigs  are  allowed  to  eat  the  grubs;  but  pigs  which  have 
never  been  pastured  are  certain  to  be  free  from  these  parasites,  and 
grubs  growing  in  fields  which  have  not  been  pastured  by  pigs  are 
likewise  certain  to  be  free  from  them.  The  use  of  such  pigs  upon 
such  fields  would  consequently  be  without  danger  from  this  source, 
and  a  little  attention  to  these  facts  will  avoid  any  injurious  conse- 
quences. That  is,  if  pigs  not  previously  allowed  to  run  out  are 
turned  into  fields  on  which  pigs  have  not  been  pastured  within  three 
years,  there  will  be  no  danger  that  they  will  become  infested  by 
these  thorn-headed  worms. 

The  general  measures  discussed  in  my  Seventh  Report  are  es- 
sentially a  destruction  of  the  May-beetles  before  they  have  laid  their 
eggs,  and  the  distribution  among  the  grubs  of  the  germs  of  their 
contagious  diseases.  Nothing  has  thus  far  been  done  to  test  the  pos- 
sibility of  the  collection  and  distribution  of  parasites  other  than 
those  of  contagious  diseases,  and  the  latter  subject  can  not  by  any 
means  be  said  to  have  been  worked  out  to  final  conclusions. 

The  May-beetles  may  be  destroyed  either  by  spraying  repeatedly 
with  arsenical  poisons  the  trees  on  whose  foliage  they  feed;  by 
shaking  or  jarring  them  down  in  the  cooler  parts  of  the  night  from 
the  trees  and  shrubs  on  which  they  are  feeding,  and  collecting  them 
for  destruction ;  and  by  trapping  and  killing  them  at  night  by  means 
of  lanterns  fastened  over  tubs  or  traps  containing  water  covered 
with  a  film  of  kerosene.  The  grubs  may  possibly  be  kept  in  check 
by  the  distribution  among  them  of  the  germs  of  their  contagious  dis- 
eases obtained  by  artificial  cultivation, — a  method  which  has  been 

*"On  an  American  Intermediate  Host  of  Echinorhynchus  sigas."  By  C.  W.  Stiles  Zool. 
An?.,  Feb.,  1892,  p  52. 


480  BULLETIN  No.  116.  [August,  1907. 

used  with  some  success  against  the  white-grubs  of  France.  The 
main  dependence  in  the  Old  World,  however,  has  been  a  thoroughly 
organized  movement  for  the  collection  of  the  beetles  from  the  trees 
at  night,  the  usual  method  of  securing  general  action  being  to  pay  a 
sufficient  price  for  the  beetles  in  quantity  to  make  their  collection  a 
profitable  enterprise  during  the  time  of  their  presence  on  the  trees. 
This  method  can  be  used  to.advantage  only  by  owners  of  very  large 
estates  or  by  communities  or  combinations  of  farmers  acting  to- 
gether for  their  common  benefit.  The  same  may  be  said  of  the 
destruction  of  the  beetles  by  poisoning  their  food.  If  the  ordinary 
land  owner  were  to  proceed  by  himself,  it  is  probable  that  his  fields 
would  become  infested  by  invasion  from  without  even  though  he 
might  destroy  every  May-beetle  on  his  own  premises.  The  least 
promising  of  these  methods  is  the  simplest  and  the  cheapest  of  them 
all — that  of  collecting  the  beetles  by  lantern  traps.  These  take  ef- 
fect much  the  most  strongly  upon  the  males,  and  collect,  under  the 
most  favorable  circumstances,  only  a  comparatively  small  percentage 
of  the  beetles  in  their  neighborhood.  Furthermore,  it  is  available 
only  on  dark  and  relatively  quiet  nights. 

What  may  be  done  by  way  of  general  concerted  action  is  well 
illustrated  by  a  campaign  of  destruction  carried  on  against  the  white- 
grubs  of  the  Swedish  province  of  Halland  during  the  ten  years  from 
1885  to  1895,  within  which  time  29,736  bushels  of  May-beetles  and 
their  larvae  were  collected  at  an  expense  of  $15,554,  or  about  52 
cents  a  bushel,  the  state  usually  paying  half  of  this  sum,  the  Eco- 
nomic Society  of  the  province  a  fourth,  and  the  communes  or  coun- 
ties the  remaining  fourth.  The  effect  was  especially  shown  in  the 
gradual  reduction  in  the  number  of  beetles  collected — from  14,- 
801  bushels  in  1887  to  5,611  in  1895,  although  the  number  of  com- 
munes participating  in  the  work  had  increased  in  the  meantime,  and 
the  area  covered  by  the  collections  was  correspondingly  greater.* 

So  far  as  is  now  to  be  foreseen,  organized  work  of  some  such  de- 
scription will  finally  be  necessary  to  the  control  of  the  white-grub 
pest  in  Illinois,  and  throughout  America  generally. 

*Aug-ust  Lyttkins,  in  Entomologlsk  Tidskrift  for  1897.    Stockholm,  1898. 


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